2...

 

“3:...“ I.
6,. I

2. .

, f5
.¢;...9»:.J
. 7 A

 

, v0.»

nun-4

 

hu 1..-

. i... . 1... I
.3. )o... . 13.. .

m
n
t
w
x
u
..

n.- alum-.ou.

I .:
... 9

1“?!

u

.310.

.mnuu-a...u.—uoo~~o

u~~nnk »,

13...?
..... in.

Int...

l"‘

. , L .

'lfi‘uvlhu‘

 

j: llll"Hill“INN”“HulllllelfllfllMlllll
W: 23AM

Michigan State
University

 

 

 

 

This is to certify that the
thesis entitled

THE DISTRIBUTION OF GUNSHOT RESIDUES GENERATED BY
DISCHARGING A FIREARM INDOORS

presented by

.Linda M. Jacobson

has been accepted towards fulfillment
of the requirements for

__M..S_.__ degree inCnmlnaJJ' ' ustice

Major pr essor

Datefl/M Jog

0-7639 MS U is an Aflirmative Action/Equal Opportunity Institution

PLACE IN RETURN BOX to remove this checkout from your record.
TO AVOID FINES return on or before date due.
MAY BE RECALLED with earlier due date if requested.

 

DATE DUE

DATE DUE

DATE DUE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

moo chlRCDaIeDuopGS—p t4

 

THE DISTRIBUTION OF GUNSHOT RESIDUES GENERATED BY DISCHARGING
A FIREARM INDOORS

By

Linda Michelle Jacobson

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Criminal Justice

2000

ABSTRACT

THE DISTRIBUTION OF GUNSHOT RESIDUES GENERATED BY DISCHARGIN G
A FIREARM INDOORS

By

Linda Michelle Jacobson

When a firearm is discharged, gunshot residue (GSR) particles leak from the
muzzle of the gun and parts of the gun near the firing hand. This airborne GSR can
deposit on nearby surfaces in addition to settling on the shooter’s hand. The purpose of
this study was to determine the distribution of GSR particles when a firearm is discharged
indoors. The type of firearm used and the number of shots fired was varied in order to
assess the impact of these factors on GSR distribution. Samples were set out to collect
GSR that might deposit two, six and ten feet to the right of the shooter. The samples
were subsequently analyzed and the number of particles related to GSR was tabulated.
The results showed that GSR particles deposited up to ten feet from the shooter in 79 out
of the 80 test fires performed. It was also found that the number of GSR particles
deposited does not add up with the number of shots fired. In comparing particle
deposition for the two firearms used in this experiment, the results showed that
discharging the semiautomatic handgun resulted in more particle deposition than the

revolver only when multiple shots were fired.

Copyright by
Linda Michelle Jacobson
2000

This research is dedicated to Mary and Michael Jacobson.

iv

TABLE OF CONTENTS

LIST OF TABLES ................................................................................. vii
LIST OF FIGURES ................................................................................ ix
INTRODUCTION .................................................................................... 1
CHAPTER 1:
GENERAL INFORMATION ON GUNSHOT RESIDUE ANALYSIS
Introduction: What is Gunshot Residue? ................................................. 3
Applications of Gunshot Residue Analysis .............................................. 6
Gunshot Residue Deposition ............................................................. 7
The Mechanism of Gunshot Residue Deposition ...................................... 8
Gunshot Residue Collection and Analysis .............................................. 9
Results and Interpretations of Gunshot Residue Tests ............................... 10
CHAPTER 2:
THE EXPERIMENT: DETERMINING THE DISTRIBUTION OF GUNSHOT
RESIDUES INDOORS
Purpose of the Study ..................................................................... 12
Applications ............................................................................... 12
Relevant Research ........................................................................ 13
Experimental Design and Methods ..................................................... 15
CHAPTER 3:
RESULTS AND INTERPRETATIONS
Results of Test Fires Using One Shot from a Revolver .............................. 18
Results of Test Fires Using Six Shots from a Revolver .............................. 22
A Comparison of the Results of One Shot and Six Shots from a Revolver ....... 27
Results of Test Fires Using One Shot from a Semiautomatic Handgun ............ 33
A Comparison of the Results of One Shot from both a Semiautomatic
Handgun and a Revolver .................................................................. 38
Results of Test Fires Using Six Shots from a Semiautomatic Handgun ........... 44
A Comparison of the Results of One Shot and Six Shots from a
Semiautomatic Handgun ................................................................... 49
A Comparison of the Results from Six Shots Fired Using a Revolver and a
Semiautomatic Handgun .................................................................. 55

CHAPTER 4

SUMMARY AND CONCLUSIONS ............................................................ 62
CHAPTER 5
SUGGESTIONS FOR FUTURE RESEARCH ................................................ 66
APPENDICES
Materials Used in this Experiment ...................................................... 67
Results of Substrate Control Examination ............................................. 68
Diagram of Room Where Experiment Performed .................................... 69
LITERATURE CITED ............................................................................ 70
GENERAL REFERENCES ...................................................................... 72

vi

LIST OF TABLES

Table 1: The distribution of particles collected after one shot from a revolver, ten feet
away from the shooter.

Table 2: The distribution of particles collected after one shot from a revolver, six feet
away from the shooter.

Table 3: The distribution of particles collected after one shot from a revolver, two feet
away from the shooter.

Table 4: Results of background particle collection prior to test fires involving one shot
from a revolver.

Table 5: The distribution of particles collected after six shots from a revolver, ten feet
away from the shooter.

Table 6: The distribution of particles collected after six shots from a revolver, six feet
away from the shooter.

Table 7: The distribution of particles collected after six shots from a revolver, two feet
away from the shooter.

Table 8: Results of background particle collection prior to test fires involving six shots
from a revolver.

Table 9: The distribution of particles collected at ten feet from the shooter after one shot
from a semiautomatic handgun.

Table 10: The distribution of particles collected at six feet away from the shooter after
one shot from a semiautomatic handgun.

Table 11: The distribution of particles collected at two feet away from the shooter after
one shot from a semiautomatic handgun.

Table 12: Results of background particle collection prior to test fires involving one shot
from a semiautomatic handgun.

Table 13: The distribution of particles collected at ten feet from the shooter after six
shots fiom a semiautomatic handgun.

Table 14: The distribution of particles collected at six feet from the shooter after six
shots from a semiautomatic handgun.

vii

Table 15: The distribution of particles collected at two feet from the shooter afier six
shots from a semiautomatic handgun.

Table 16: Results of background particle collection prior to test fires involving six shots
from a semiautomatic.

Table 17: Results of substrate control samples collected for each batch of carbon tape
used in this experiment.

viii

LIST OF FIGURES

Figure 1: An EDX spectrum of a GSR particle containing lead, barium and antimony.
Figure 2: A GSR particle as seen using an SEM.

Figure 3: The distribution of unique GSR particles deposited at three distances from the
shooter afier one shot fi'om a revolver.

Figure 4: The distribution of particles consistent with GSR deposited at three distances
from the shooter after one shot from a revolver.

Figure 5: The distribution of unique gunshot residue particles deposited at three
distances from the shooter after six shots from a revolver.

Figure 6: The distribution of particles consistent with gunshot deposited at three
distances fi'om the shooter after six shots from a revolver.

Figure 7: A comparison of the number of unique GSR particles collected at two feet
from the shooter after one shot and afier six shots were fired from a revolver.

Figure 8: A comparison of the number of unique GSR particles collected at six feet from
the shooter after one shot and after six shots were fired from a revolver.

Figure 9: A comparison of the number of unique GSR particles collected at ten feet from
the shooter after one shot and after six shots were fired from a revolver.

Figure 10: A comparison of the number of particles consistent with GSR collected at
two feet from the shooter after one shot and after six shots were fired from a revolver.

Figure 11: A comparison of the number of particles consistent with GSR collected at six
feet from the shooter afier one shot and after six shots were fired from a revolver.

Figure 12: A comparison of the number of particles consistent with GSR collected at ten
feet from the shooter after one shot and after six shots were fired from a revolver.

Figure 13: The distribution of unique GSR particles deposited at three distances from
the shooter after one shot from a semiautomatic handgun.

Figure 14: The distribution of particles consistent with GSR deposited at three distances
fi'om the shooter after one shot from a semiautomatic handgun.

ix

Figure 15: A comparison of the number of unique GSR particles collected at two feet
from the shooter after one shot was fired from a revolver and a semiautomatic handgun.

Figure 16: A comparison of the number of unique GSR particles collected at six feet
from the shooter after one shot was fired from a revolver and a semiautomatic handgun.

Figure 17: A comparison of the number of unique GSR particles collected at ten feet
from the shooter after one shot was fired from a revolver and a semiautomatic handgun.

Figure 18: A comparison of the number of particles consistent with GSR collected at two
feet from the shooter after one shot from a revolver and a semiautomatic handgun.

Figure 19: A comparison of the number of particles consistent with GSR collected at six
feet from the shooter after one shot from a revolver and a semiautomatic handgun.

Figure 20: A comparison of the number of particles consistent with GSR collected at ten
feet from the shooter after one shot from a revolver and a semiautomatic handgun.

Figure 21: The distribution of unique GSR particles deposited at three distances from
the shooter after six shots from a semiautomatic handgun.

Figure 22: The distribution of particles consistent with GSR deposited at three distances
from the shooter after six shots from a semiautomatic handgun.

Figure 23: A comparison of the number of unique GSR particles deposited at two feet
from the shooter after firing one and six shots from a semiautomatic handgun.

Figure 24: A comparison of the number of unique GSR particles deposited at six feet
from the shooter after firing one and six shots from a semiautomatic handgun.

Figure 25: A comparison of the number of unique GSR particles deposited at ten feet
from the shooter after firing one and six shots from a semiautomatic handgun.

Figure 26: A comparison of the number of particles consistent with GSR deposited at 2
ft from the shooter after firing one and six shots from a semiautomatic handgun.

Figure 27: A comparison of the number of particles consistent with GSR deposited at 6
ft from the shooter after firing one and six shots from a semiautomatic handgun.

Figure 28: A comparison of the number of particles consistent with GSR deposited at
10 ft from the shooter after firing one and six shots from a semiautomatic handgun.

Figure 29: A comparison of the number of unique GSR particles deposited at 2 it from
the shooter after firing six shots from a semiautomatic handgun and a revolver.

Figure 30: A comparison of the number of unique GSR particles deposited at 6 it from
the shooter after firing six shots from a semiautomatic handgun and a revolver.

Figure 31: A comparison of the number of unique GSR particles deposited at 10 ft from
the shooter after firing six shots from a semiautomatic handgun and a revolver.

Figure 32: A comparison of the number of particles consistent with GSR deposited at 2
ft from the shooter after firing six shots from a semiautomatic handgun and a revolver.

Figure 33: A comparison of the number of particles consistent with GSR deposited at 6
ft from the shooter after firing six shots from a semiautomatic handgun and a revolver.

Figure 34: A comparison of the number of particles consistent with GSR deposited at 10
it from the shooter after firing six shots from a semiautomatic handgun and a revolver.

Figure 35: Diagram of room where test fires were performed, not to scale.

xi

INTRODUCTION

When a firearm is discharged, gunshot primer residue (GSR) particles leak from
the muzzle of the gun and parts of the gun near the firing hand. This airborne GSR can
deposit on nearby surfaces in addition to settling on the shooter’s hand. The collection of
GSR from someone’s hand indicates that the individual either discharged a firearm,
handled a gun that was recently fired, came into contact with a surface contaminated with
GSR, or was in close proximity to a firearm while it was discharged.

Research has shown that GSR can deposit on a non-shooter’s hand held close to a
discharging firearm, or on surfaces close to the shooter. To date, these studies have been
limited to sampling areas in close proximity to the shooter (within three feet), or in
experiments involving sampling farther away from the shooter, the tests were not
repeated to demonstrate their reliability.

This purpose of this study is to determine the distribution of GSR particles when a
firearm is discharged indoors in a standard sized room (i.e. how far the particles travel,
how many particles deposit, etc.). The number of shots fired and the type of gun used
was varied in order to see if these factors impact the distribution of GSR indoors.
Adhesive collection disks were set out two feet, six feet, and ten feet to the right of the
shooter and were left out to collect particles depositing for a five minute period after the
firearm was discharged. The disks were then analyzed for traces of GSR using Scanning
Electron Microscopy coupled with Energy Dispersive X-ray analysis (SEM/EDX), and

the GSR particles found were tabulated.

This study will provide valuable insight into how far GSR travels from a firearm
that is discharged indoors. The results of this study will benefit GSR analysts responsible
for interpreting the results of tests to determine if GSR was present on a shooting
suspect’s hand. This study will also aid prosecutors, defense attorneys, and judges faced
with the interpretation of GSR evidence in the courtroom.

Knowing the amount GSR that can deposit on objects at certain distances from a
discharging firearm can indicate the potential for GSR transfer to individuals coming into
contact with these objects. For example, can a non-shooter transfer GSR to their hands
by merely touching an object in a room where a shooting occurred? If the adhesive
collection disks used in this experiment are looked at as an individual standing in a room
where a firearm was discharged, the potential for GSR settling on the hands of a non-
shooter can be evaluated. All of these factors impact the interpretation of GSR test
results. Overall, this study aims to help estimate the potential for GSR contamination on

the hands of those present at or near the time of a shooting.

Chapter 1

GENERAL INFORMATION ON GUNSHOT RESIDUE ANALYSIS

Introduction: What is Gunshot Residue?

Discharging a firearm releases an assortment of particulate matter and vapors into
the surrounding area. The particles that result are termed gunshot primer residues (GSR),
and these residues emerge from both the muzzle of the firearm and parts of the gun near
the firing hand. Gunshot primer residue particles are those which contain lead (Pb),
barium (Ba) and possibly antimony (Sb) and have spheroidal morphology. As a firearm is
discharged, GSR combines with propulsive gases and can deposit on nearby objects as
well as on the shooter (Krishnan, 1982; Meng & Caddy 1997; Basu, Boone, Denio, &
Miazga, 1997; Wolten, Nesbitt, Calloway, Loper, & Jones, 1977, 1979a).

Law enforcement agencies can sample a suspected shooter’s hand for traces of
GSR and send it to a crime laboratory for analysis. At the lab, the sample will be
analyzed for traces of GSR using Scanning Electron Microscopy coupled with Energy
Dispersive X-ray Analysis (SEM/EDX). The test results can indicate whether or not an
individual could have discharged a firearm.

The best way to identify GSR is by elemental content. Most cartridge case
primers contain lead (Pb), barium (Ba), and antimony (Sb) (ASTM Method E-1588,
Thornton, 1994; Meng & Caddy, 1997; Wolten et a1., 1977). The compositional criteria

for GSR particles that outlines the types of particles searched for during analysis was first

detailed in a report issued by the Aerospace Corporation in 1977. An updated version of
this list appears in the American Society for Testing and Materials method E—1588-95:
Particle compositions unique to GSR:

1) Lead (Pb), antimony (Sb), barium (Ba)

2) Antimony, barium

Particle compositions consistent with GSR but not unique to it:

1) Barium, calcium, silicon with a trace of sulfur

2) Lead, antimony

3) Lead, barium

4) Lead

5) Barium

Lead and small amounts of antimony can be found in bullets, while barium, lead, and
higher amounts of antimony are found in the primer. Other elements commonly found in
GSR particles are silicon, calcium, aluminum copper, iron, sulfur, phosphorous, zinc (if
there is a higher amount of copper present), nickel (if copper and zinc are present),
potassium, chloride, and tin (found in obsolete ammunition). The presence of other
elements indicates that a particle did not originate from GSR. This classification scheme

has been adopted in general by forensic scientists dealing with GSR analysis. An EDX

spectrum from a particle containing lead, barium and antimony appears in Figure 1.

 

cps
100‘ ‘
3 Pb
50 .1
Sb
1 I 88
r
U .
FC '1 9-. 8L
' u
Kaila? qt
! g 7': Ba 3
' Sfibfil‘ ‘V
(Sufi " 1 It fia Pb
" ' m‘aw .. 393% P”
0 - I ‘ . - .‘M‘ ww‘fif‘fr -- r..- .__.._
0 5 10 15 20
Energy (keV)

 

 

 

Figure 1: An EDX spectrum of a GSR particle containing lead, barium and antimony.

In addition to particle composition, morphology is another criteria used by
analysts when evaluating GSR evidence. GSR particles are predominantly spheroidal in
shape, as they result from rapid condensation from a vapor state (Basu, 1982; Meng &
Caddy, 1997; Wolten et al., 1977, 1979a; Basu & Ferris, 1980). 70% to 100% of GSR
particles are spheroidal. Other shapes of GSR particles include irregular particles and
clusters, which are formed from many spheroids clumping together (Wolten et al., 197 7,

1979a). A picture demonstrating the typical morphology of GSR particles appears in

Figure 2.

 

Accv Spot Magn Det WD I—————'I 2pm

20.0kV 6.0 l3760x 88E 10.0

 

 

 

 

Figure 2: A GSR particle as seen using an SEM.

Applications of Gunshot Residue Analysis

GSR can be used to determine many things, but is primarily used to determine
whether or not an individual could have discharged a firearm. GSR on the hands of a
suspect may indicate whether or not the individual may have discharged or handled a
recently discharged firearm, or have been present when a firearm was discharged. In
situations where a suspect denies handling a firearm, the presence or absence of GSR on
his or her hands may support or contradict their statement (Thornton, 1994; Meng &
Caddy 1997; Krishnan, 1982). Other uses for GSR include reconstructing events that
took place at the time of a shooting, as GSR can be used to identify bullet holes and
possibly to estimate firing distances (Krishnan, 1982; Meng & Caddy, 1997; Thornton,

1994; Renfro & Jester, 1973).

Gunshot Residue Deposition

The GSR deposited on the hands of a shooter of a revolver or pistol comes from
three main sources: the gap between the cylinder and rear end of the barrel, the ejection of
the cartridge, and blow-back from the muzzle cloud (Meng & Caddy, 1997; Basu etal.,
1997; Krishnan, 1982). In addition to depositing on the shooter, GSR can deposit on
surfaces close to the firearm including individuals or objects in close proximity (Meng &
Caddy, 1997; Basu et al., 1997; Krishnan, 1982; Thornton, 1986).

Many factors can influence the amount and distribution of GSR deposited when a
firearm is discharged. Among these factors are the type and condition of the weapon, the
ammunition, the number of shots fired, the type of surface on which the GSR is
deposited, and the direction and force of air currents (Krishnan, 1982; Meng & Caddy,
1997)

Even if the same gun and ammunition type is used, the amount of GSR deposited
can vary from shot to shot. Gunshot residues are products of combustion and are ejected
from the gun as a result of the pressure generated in the gun. Any variation in this
chamber pressure can impact the velocity of the gases and solids ejected from the gun,
which can in turn impact the distribution of these products of combustion. Differences in
the ammunition may be found in the weight of the primer, the physical condition of the
primer, the condition and weight of the bullet, and the primer cup hardness (Munhall,
1961). Even within the same box of ammunition, differences in velocity and pressure can

be found (Krishnan, 1977). Inconsistencies contributed by the firearm itself may arise

from firing pin blows that vary in strength, or, in revolvers, misalignment of the chambers
with the barrel (Munhall, 1961).

The deposition of GSR resulting from multiple shots can also be inconsistent. A
number of successive firings do not necessarily increase the amount of GSR deposited.
The amount of GSR deposited does not always add up with the number of shots fired

(Basu et al., 1997; Krishnan, 1977).

The Mechanism of Gunshot Residue Deposition

Much research has been devoted to determining the mechanism of GSR deposition,
particularly on the distribution of up-range GSR (GSR deposited on surfaces close to the
firearm) (Thornton, 1994). Research done by Renfro and Jester on the length of time
GSR remains suspended in the air after shooting suggests that GSR settling from the air
may deposit on a shooter’s hand (Renfro & Jester, 1973; Basu et al., 1997). Other
researchers disagree with this, proposing that the GSR found on a shooter’s hand is force-
deposited there at the time of discharge (Basu etal., 1997; Wolten et al., 1977).

In considering the mechanism of GSR deposition, the potential for GSR settling
on an individual other than the shooter must be addressed. Handling a recently
discharged firearm can transfer to an individual’s hand levels of GSR similar to those
found on a shooter’s hand. Studies done by Thornton showed that a hand held in close
proximity to a discharging firearm intercepts a level of antimony consistent with having
fired or handled a gun. This result was based on eight test fires with a .22 caliber

revolver during which the hand of a non-shooter was held two inches laterally from the

cylinder (Thornton, 1986). Another situation, which provides a potential source for GSR
found on the hands of a non-shooter, is secondary transfer. The secondary transfer of
GSR to an individual’s hand from some other surface on which GSR is deposited is also
possible (Thornton, 1994). Overall, one must proceed with caution when interpreting the

results obtained while testing for the presence of GSR on an individual’s hands.

Gunshot Residue Collection and Analysis

When a suspect is arrested in connection to a crime involving a firearm, his or her
hands may be sampled for the presence of GSR. Most law enforcement agencies use
some type of adhesive tape, commonly referred to as a stub, to collect particles from a
suspect’s hand. The adhesive is pressed repeatedly against the areas of interest, and after
a brief questionnaire is filled out, the sample is submitted to a laboratory for analysis.

If a conductive adhesive is used, the sample taken can be analyzed directly using
Scanning Electron Microscopy combined with Energy Dispersive X-ray Analysis
(SEM/EDX). Using this method, the morphology of the particles can be obtained in
addition to their elemental characteristics. (Wolten et al., 1977; Meng & Caddy, 1997;
Krishnan, 1982; Thornton, 1994). If the SEM/EDX system is automated, the system will
scan the sample, analyze the particles with a backseatter electron image as determined by
pre-set thresholds, identify the elements present in the particle, and record its coordinates.
The operator can then later return to the particles of interest and confirm their elemental

composition by reviewing the EDX spectra (Thornton, 1994; Germani, 1991).

The SEM/EDX analysis of a GSR sampling stub can be very time consuming
(approximately 4-10 hours) depending on the instrument being used and the number of
particles present. The adhesive stubs used by most labs are approximately one half inch
in diameter, and because of lengthy analysis time, the Operator may choose to analyze the
entire stub surface or just a percentage of it. In a recent poll it was found that most labs
analyze 50% or more of the stub surface before confirming a negative result, but this
percentage can vary from lab to lab (Singer, 1996).

The number of unique GSR particles required to yield a positive result also varies
from lab to lab. Afier finding one unique GSR particle some labs consider the sample
positive for the presence of GSR. Other labs require a higher threshold for the number of
unique GSR particles required to obtain a positive result (Singer, 1996).

There are four possible outcomes for a GSR exam. If the examination was not
inconclusive, the laboratory report will state that no particles consistent with GSR were
found, or that particles consistent with GSR were found, or that particles unique to GSR
were found. The collection of GSR from someone’s hand indicates that the individual
either discharged a firearm, handled a gun that was recently fired, came into contact with

a surface contaminated with GSR, or was in close proximity to a firearm while it was

discharged.

Results and Interpretation of Gunshot Residue Tests

Analysts must consider many factors in interpreting GSR test results. Particles

that individually resemble GSR are produced by many industries. The trace elements Pb,

10

Sb and Ba are present in many materials. Auto exhaust, batteries, plumbing materials,
gasoline, glass, and solder all contain lead (Thornton, 1994; Wolten et al., 1977;
Krishnan, 1982). Paint, grease, rubber and lubricating oils may contain barium. Finally,
environmental sources of antimony include batteries, enamels, bearings, and lead alloys
(Thornton, 1994; Krishnan, 1982).

Although lead, barium and antimony are found individually in various
environmental sources, the occurrence of all three together is very rare (Krishnan, 1982;
Wolten et al., 197 7). In addition, the particles that individually resemble GSR that are
produced by many industries also contain elements that are not consistent with GSR. For
example, lead with bromine is indicative of automobile exhaust, and lead with titanium
might indicate lead-based paint. When the criteria for GSR composition was developed
by Wolten et al., the hands of individuals in occupations dealing with metals or
compounds containing Pb, Sb and Ba were sampled. Among the occupational groups
sampled were lead smelters, auto mechanics and battery assemblers. None of the samples
taken contained any particles considered to be unique to GSR (Wolten et al., 1977,
1979b; Zeichner, 1997).

Another important factor for analysts to consider is the time delay between when
the shooting occurred and the hand sampling was done. GSR particles on a person’s
hands can be lost through washing and coming into contact with other objects. The
absence of GSR on an individual’s hand might be explained by a time delay of four or
more hours between the incident and the sampling, or by the activities the individual was

involved in since the shooting.

11

Chapter 2

THE EXPERIMENT: DETERMINING THE DISTRIBUTION OF GUNSHOT
RESIDUES INDOORS

The Purpose of this Study

This experiment was designed to estimate the distribution of gunshot residues
(GSR) generated by a firearm that is discharged indoors (i.e. how far the particles travel,
how many particles deposit, etc.). The distribution of GSR over three fixed distances to
the right of the shooter was examined. The type of firearm used and the number of shots
fired were varied, and the impact of these variations on the deposition of GSR was

examined.

Applications

This study will provide valuable insight into how far GSR can travel from a
firearm that is discharged indoors. The study will also shed light onto the potential for
GSR contamination on the hands of those present at or near the time when a firearm is
discharged indoors. In addition, this experiment can aid in answering questions typically
put forth to GSR analysts in court such as: When a firearm is discharged indoors and

individuals other than the shooter are present, is it possible that the hands of those who

12

had no contact with the firearm could be contaminated with GSR? If so, how far away
from the shooter can individuals be and still pick up GSR on their hands? Is it possible
for an individual to get GSR on their hands by touching objects in a room where a firearm
was discharged? If so, how far away from the firearm are these surfaces that collect GSR
located? Studies such as this one are essential for analysts answering these types of
questions.

This experiment will provide useful information for criminalists interpreting the
results of hand samples taken from potential shooters. Crime scene reconstructionists
faced with recreating details of an indoor shooting will also benefit from this study. In
addition, investigators, prosecutors, defense attorneys, judges, and other individuals that

need to interpret GSR evidence in the courtroom will find this study useful.

Relevant Research

This study was designed after considering previous research done on gunshot
residue distribution. The research done in this area is severely lacking, and there is a
definite need for more thorough studies on gunshot residue distribution.

Specifically, there has been little research done on the distribution of gunshot
residues generated by a firearm that was discharged indoors. In 1987, White and Gross
began a study on the deposition of GSR at varying distances from a discharging firearm.
Their study employed different types of firearms that were discharged in both indoor and
outdoor shooting ranges. Although their study focused on the deposition of GSR

downrange from the firearm, in one of their test fires, the distribution of GSR to both

13

sides and behind the shooter was examined. After firing a Smith and Wesson two-inch
.38 caliber handgun, the residues 4ft, 6ft and 8ft to the right, left and behind the shooter
were sampled. White and Gross calculated the ratios of particles identified as “consistent
with” GSR and “unique to” GSR. The results showed that the ratio of “unique” to
“consistent with” GSR particles decreased as the distance from the shooter increased.
Unfortunately this part of their experiment was not duplicated to demonstrate
repeatability, and because of this it is difficult to draw any firm conclusions from their
results.

In 1976, Seamster et a1. conducted studies on the spatial distribution of firearms
discharge residues. After firing a Colt revolver with 38 Special ammunition, “fallout
residues” were sampled from the floor 311 to the right and 4ft ahead of the shooter. The
most intense collection of fallout residues was found 2ft to the right and 3ft ahead of the
shooter. Unfortunately this experiment was only performed once and the dimensions of
the room used are not mentioned in the published results. The dimensions of the room
may impact the amount of GSR deposited certain distances from the firearm, and
repeating the experiment is necessary in order to show a pattern and draw reliable
conclusions from their results.

The final study done which incorporated the analysis of GSR travelling to the
sides of the shooter was conducted by the Aerospace Corporation in 1977. In the
Aerospace study individuals were placed 3ft and 10ft abreast of and in line with the
shooter. After a .22 caliber, short-barreled revolver was discharged the hands of those
individuals standing next to the shooter were tested for GSR. The results showed that

those standing 3ft from the shooter had GSR on their hands while those standing 10ft

14

away did not. The published results indicate that this experiment was performed more
than once, but the specific number of times is not mentioned. The results also failed to
report whether the firearm was discharged indoors or outside.

It is obvious that there is a need for further study on the distribution of gunshot
residues indoors. More thorough studies with repeated trials and carefully documented

experimental conditions would be of great value to those dealing with GSR evidence.
Experimental Design and Methods

Two firearms were used in this experiment: a Ruger .357 Blackhawk revolver and
a Smith and Wesson 9mm semiautomatic handgun. Winchester 38 Special, Super X, 110
grain hollow point ammunition was used for all test firings using the revolver.
Winchester 9mm Luger 115 grain hollow point was used for all test firings in which the
semiautomatic was used (see Appendix A for a complete list of the materials used in this
experiment). All of the test firings were done in the same draft-free room of
approximately 195 square feet (See Appendix C for a room diagram). The firearms used
were cleaned prior to each test firing, and the room used was cleaned and aired out
between each shooting. The test fires were spaced at least 24 hours apart.

Airborne GSR generated from each firearm was collected after one shot was fired,
and after firing 6 shots. The test fires for each experimental setup were repeated five
times.

The airborne GSR was collected using carbon tape specimen mounts set up 2ft,

6ft and 10ft horizontally to the right of the shooter. The collection distances were chosen

15

after considering the size limitations of the room in addition to the past research done in
this area, where the samples have not been taken past ten feet from the shooter. The
specimen mounts were placed in line with the shooter’s hand, and one foot vertically
below the level of the shooter’s hand. The specimen mounts were exposed for particle
collection just before the shots were fired, and remained exposed for particle collection
for five minutes afier the shots were fired.

As a negative control, one carbon tape specimen mount was left exposed for a
five-minute period prior to each test firing to collect “background” particles. In addition,
one unused specimen mount from each batch of carbon tapes used in this experiment was
analyzed as a substrate control (see Appendix B for these results). Including the substrate
control collections, 82 samples were generated in this experiment.

The specimen mounts were analyzed directly using SEM/EDX. Two instruments
were used: a Phillips XL30 Scanning Electron Microscope equipped with an Oxford ISIS
300, and an R.J. Lee Personal SEM. The instruments were programmed to search for
particles containing lead, barium and antimony. Fifty percent of each 1.2 cm diameter
specimen mount was analyzed, and in that area the number of those particles in the
following 2 categories were tabulated:

1) Particles unique to GSR:

i) Pb-Sb-Ba
ii) Sb—Ba

2) Particles consistent with GSR:

i) Pb-Ba
ii) Pb-Sb
iii) Pb only
iv) Ba only

The EDX spectra were reviewed for the particles tabulated. See Figure 1 for an EDX

spectrum of a known GSR particle containing Pb, Sb and Ba.

17

Chapter 3

RESULTS AND INTERPRETATIONS

Results of Test Fires Using One Shot from a Revolver

In test fires using one shot from a revolver, unique GSR particles were found two,
ten and six feet from the shooter in all trials. The numbers of unique GSR particles
collected in each category are tabulated in Tables 1 through 4. The distribution of these
particles was inconsistent. In four out of the five trials, the highest numbers of unique
GSR particles was deposited two feet from the shooter. However, at six and ten feet from
the shooter, the number of particles deposited did not always decrease as the distance
from the shooter increased. For example, in two out of the five trials, more unique GSR
particles were deposited at ten feet from the shooter than were deposited at six feet. A
graph of these results appears is Figure 3. The total number of particles unique to GSR
deposited varied from 1 to 14 at ten feet away from the shooter, from 2 to 8 at six feet
away from the shooter, and from 1 to 30 at two feet away from the shooter.

Particles consistent with GSR were also deposited at all three distances from the
shooter in all five trials. Tabulations of the particles collected that were consistent with
GSR appear in Tables 1 through 4. The distribution of these particles over the three
collection distances varied. In all of the trials, the number of particles consistent with
GSR collected was always significantly higher two feet from the shooter than at the other
two distances. However, at six and ten feet from the shooter, the number of particles

deposited did not always decrease as the distance from the shooter increased. For

18

example, in two out of the five trials more particles consistent with GSR were collected at

ten feet from the shooter than at six feet. In the remaining two trials, the number of

particles collected that were consistent with GSR did not relate to the distance from the

shooter. A graph of these results appears in Figure 4. The total number of particles

consistent with GSR that were deposited varied from 4 to 196 at ten feet away from the

shooter, from 13 to 299 at six feet away from the shooter, and from 149 to 1221 at two

feet away from the shooter.

Table l: The distribution of particles collected after one shot from a revolver, ten feet

away from the shooter.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
I shot particles with GSR
revolver
Trial 1 5 0 0 7 107 1 5 115
10 it away
Trial 2 0 1 0 1 3 0 1 4
10 ft away
Trial 3 2 0 0 0 20 0 2 20
10 ft away
Trial 4 7 7 0 7 1 0 14 8
10 ft away
Trial 5 1 1 1 7 1 86 2 2 196
10 ft away

 

 

 

 

 

 

 

 

 

19

 

Table 2: The distribution of particles collected after one shot from a revolver, six feet

away from the shooter.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
I shot Particles with GSR

revolver
Trial 1 1 2 0 4 16 0 3 20

6 it away
Trial 2 2 1 0 7 10 0 3 17

6 ft away
Trial 3 6 0 0 2 10 1 6 l3

6 it away
Trial 4 3 5 0 8 4 5 8 17

6 it away
Trial 5 2 0 0 12 284 3 2 299

6 ft away

 

 

 

 

 

 

 

 

 

Table 3: The distribution of particles collected after one shot from a revolver, two feet

away from the shooter.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
I shot Particles with GSR

revolver
Trial 1 26 4 O 14 891 10 30 915
2 it away

Trial 2 3 1 0 14 135 0 4 149
2 ft away

Trial 3 9 5 0 21 198 2 14 1221
2 ft away

Trial 4 22 5 O 32 784 0 21 816
2 ft away

Trial 5 0 1 3 35 1162 3 1 1203
2 ft away

 

 

 

 

 

 

 

 

 

20

 

 

Table 4: Results of background particle collection prior to test fires involving one shot
from a revolver.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
I shot Particles with GSR
revolver
Trial 1 0 O 0 0 O 0 0 0
background
Trial 2 0 0 0 0 0 0 0 0
background
Trial 3 O 0 0 0 0 0 0 0
background
Trial 4 0 0 0 0 0 0 0 0
background
Trial 5 0 0 0 0 0 0 0 0
background
1 shot revolver: distribution of unique GSR particles
35 - -
30 ,
8 25 .. . -. _ -_-».,-. - .
:3 1+ 1 shot revolver trial 1
25. 20 «
' £- , 1+1 shot revolver trial 2
g 15 J
f .ra: 1+1 shot revolver trial 3
l g 10 1 . i
‘ —)(— 1 shot revolver trial 4
5 ‘ I‘
‘ A 3 .+1 shot revolver trial 5
o ‘. I- I- I. -- z .. 2.- .I g -
2ft 6ft 10ft * # i“

distance from shooter

Figure 3: The distribution of unique GSR particles deposited at three distances from the
shooter after one shot from a revolver. I

21

 

1 shot revolver: distribution of particles consistent with GSR

 

1400
1200.
,% 1°°° l¥13h&'é§oflefnfi'i *
l E 800 ‘_._ 1 shot revolvertrial2
a I ‘ o
‘ “5 1+1 shot revolvertrralB
g 600 ‘__,._ 1 shot revolvertrial4
E i+lshotrevolvertria15 ‘-
2 400 . - _- ,___g_-_ ,_
200
0 ______~_-._

 

 

 

 

Zfl 6fl 10fl
distance from shooter

Figure 4:? The distrtibution’of particles consistent with GSR deposited at three distances
from the shooter after one shot from a revolver.

Results of Test Fires Using Six Shots from a Revolver

In test fires using six shots from a revolver, particles unique to GSR were found
two, six and ten feet way from the shooter in all trials. The distribution of these particles
is tabulated in Tables 5 through 8. The distribution of unique GSR particles in these trials
was inconsistent. In three out of the five trials, the number of unique GSR particles
decreased as the distance from the shooter increased. However, in the remaining two
trials, the number of unique GSR particles collected did not relate to the distance from the

shooter. For example, in trial one, more unique GSR particles were deposited ten feet

22

from the shooter than were deposited two and six feet away. In three out of the five trials,
the highest number of unique GSR particles was deposited two feet away from the
shooter. A graph of these results appears in Figure 5. The total number of unique GSR
particles that was deposited varied from 1 to 47 at ten feet away from the shooter, from
10 to 24 at six feet away from the shooter, and from 29 to 147 at two feet away from the
shooter.

Particles consistent with GSR were found at all three distances from the shooter in
all trials. The distribution of the particles collected is tabulated in Tables 5 through 8.
The distribution of these particles varied. In three out of the five trials the number of
particles consistent with GSR that were deposited decreased as the distance from the
shooter increased. In the other two trials, the number of these particles deposited did not
relate to the distance. For example, in trial one, more particles consistent with GSR were
deposited at six feet from the shooter than at two feet away. In comparing the five trials,
the highest number of particles deposited 2 it away from the shooter in four trials. A
graph of these results appears in Figure 6. The total number of particles consistent with
GSR that were deposited varied from 18 to 793 at ten feet away from the shooter, from

156 to 1508 at six feet away from the shooter, and from 369 to 2225 at two feet away

from the shooter.

23

Table 5: The distribution of particles collected after six shots from a revolver, ten feet

away from the shooter.

 

Pb, Ba

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
6 shots particles with GSR
revolver
Trial 1 26 7 0 23 767 3 33 793
10 ft away
Trial 2 29 18 0 7 104 0 47 111
10 ft away '
Trial 3 9 5 0 9 207 1 14 217
10 ft away
Trial 4 0 1 0 1 17 0 1 18
10 it away
Trial 5 13 5 0 7 217 0 18 224
10 ft away

 

 

 

 

 

 

 

 

 

Table 6: The distribution of particles collected after six shots from a revolver, six feet

away from the shooter.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles I
name Ba GSR consistent
6 shots Particles with GSR
revolver
Trial 1 13 4 0 65 1441 2 17 1508
6 it away
Trial 2 3 7 0 50 180 2 10 232
6 ft away
Trial 3 9 6 0 10 145 l 15 156
6 it away
Trial 4 ll 5 1 5 271 9 16 286
6 ft away
Trial 5 19 5 0 33 445 2 24 480

6 ft away

 

 

 

 

 

 

 

 

 

24

 

 

Table 7: The distribution of particles collected after six shots from a revolver, two feet

away from the shooter.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name Ba GSR consistent
6 shots Particles with GSR
revolver
Trial 1 22 7 0 29 1161 2 29 1192
2 it away
Trial 2 35 12 O 245 1033 2 47 1280
2 ft away
Trial 3 33 32 0 41 314 14 65 369
2 ft away
Trial 4 108 39 2 55 2155 13 147 2225
2 ft away
Trial 5 66 24 2 76 1826 44 90 1948
2 ft away

 

 

 

 

 

 

 

 

 

Table 8: Results of background particle collection prior to test fires involving six shots
from a revolver.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
6 shots Particles with GSR
revolver
Trial 1 0 0 0 0 0 0 0 0
background
Trial 2 O 0 0 0 0 0 0 0
background
Trial 3 0 0 0 0 0 0 O 0
background
Trial 4 0 0 0 0 0 0 0 0
background
Trial 5 0 0 O 0 0 0 0 0
background

 

 

 

 

 

 

 

 

 

25

 

 

6 shots revolver. tistn'bllion of mm (ER particles

160

 

140.

120

1(1)-

number of particle

35858

 

 

O

 

 

‘7

d'utance from shooter

""_.:‘6”sliS§re€1»€ririlff
R_.._6shotsrworuertriarz ~
j+6slntsrevohrertrial3
1+6slntsrevohertr'nl4 *
1+6slntsrewhieru'h15

Figure 5: The distribution of unique GSR particles deposited at three distances fi'om the I A

shooter after six shots from a revolver.

26

6 shots revolver: thtrihttion of particles canister! with GSR

 

 

 

 

 

2500

2000.
. é _; sasamawrar
. “5 1+6shotsremh/ertrial3
1 S w+6slntsrevolxertr°n15
a -- -_.,- i____ ,______-__L -

500,

0 . .
2ft 6h 10ft
(Etame fromshooter

Figure 6: ThedistributioTr of particles consistent with GSR deposited at three distances
from the shooter after six shots from a revolver.

A Comparison of the Results of One Shot and Six Shots from a Revolver

The trend for the number of particles deposited after one shot and after 6 shots
from a revolver differed for the unique GSR particles and for the particles consistent with
GSR. Graphs of these results appear in Figures 7 through 12. The tabulations of unique
GSR particles showed that more particles were generally deposited after six shots were
fired than after one shot. The tabulations of particles consistent with gunshot residue

showed that more particles were deposited ten feet and six feet away from the shooter

27

afier six shots were fired. However, two feet from the shooter, the tabulations of particles

consistent with GSR deposited were similar after both one and six shots were fired.

Unique GSR particle counts from revolver: 1 shot vs. 6 shots at 2 ft

from shooter

 

number Br particle

 

 

 

Figurei7: A comparison “of the number of unique GSR particles collected at two-feet
from the shooter after one shot and after six shots were fired from a revolver.

28

Unique GSR particle counts from revolver: 1 shot vs. 6 shots at 6 ft

from shooter

 

number of particle

 

 

 

Figure 8: A comparison of the number ofirnique GSRpartiEIes collected at six feet from
the shooter after one shot and after six shots were fired from a revolver.

29

Unique GSR particle counts from revolver: 1 shot vs. 6 shots at
10 ft from shooter

 

number of particle

 

 

 

Figure 9: A comparison of the number of unique GSR particles collected at tenfwai'om
the shooter after one shot and after six shots were fired from a revolver.

30

 

number of particle

 

 

 

Figure T0: A comparison of the numbers of particles corisisfent with GSchollected’ at

two feet from the shooter after one shot and after six shots were fired from a revolver.

31

Number of particles consistent with GSR collected 6 ft from
shooter: 1 shot vs. 6 shots from a revolver

1600
1400 ..
1200 .
1000 - f .
800

600 . -
400 -- .. .

200

 

A number of particle

 

 

 

 

Figure 11: A comparison of the numbers of particles consistent with GSR collected at
six feet from the shooter afier one shot and after six shots were fired from a revolver. .

32

Number of particles consistent with GSR collected 10 ft from
shooter: 1 shot vs. 6 shots from a revolver

900
800 7 - -.
700---- _ _‘
600 -__ - ,. . - .
500 -V- . . ,, - ._ ,, -. . .- -
400 . . = .1 ,. _ _

300-- -- . - - , - . . -
200 -W - - - - , ,_

1004 --._
0-1.

 

 

number of particle

 

 

 

 

 

Figure 12: A comparison of the numbers of particles consistent with GSR collected at
-ten feet from the shooter after one shot and after six shots were fired from a revolver.

 

Results of Test Fires Using One Shot from a Semiautomatic Handgun

In test fires using one shot from a semiautomatic handgun, particles unique to
GSR were found at all three distances from the shooter in four out of five trials. In one
trial, no unique GSR particles were deposited ten feet from the shooter, but they were
deposited two and six feet away. The number and identity of the unique GSR particles
that were collected are tabulated in Tables 9 through 12. Overall, the distribution of these
particles was inconsistent. In two out of the five trials, the number of unique GSR
particles deposited decreased as the distance from the shooter increased. In the remaining

three trials, the number of these particles deposited did not relate to the distance from the

33

shooter. For example, in trial five, more unique GSR particles were collected six feet
from the shooter than were collected two feet away. In addition, in four out of the five
trials, the highest number of unique GSR particles was deposited 2 feet away from the
shooter. A graph of these results appears in Figure 13. In comparing the five trials, the
number of unique GSR particles collected varied from 9 to 107 particles at two feet away
from the shooter, from 2 to 21 particles at six feet away from the shooter, and from 0 to 9
particles at ten feet away from the shooter.

Particles consistent with GSR were deposited at all three distances from the
shooter in all five trials. The number and identity of these particles are tabulated in
Tables 9 through 12. In four out of the five trials, the number of particles collected
decreased as the distance from the shooter increased. In the remaining trial, the number
of particles deposited did not relate to the distance from the shooter. A graph of these
results appears in Figure 14. In comparing the five trials, the number of particles
consistent with GSR that were collected varied from 45 to 8846 particles at two feet away
from the shooter, from 33 to 760 particles at six feet away from the shooter, and from 1 to

203 particles at ten feet away fi'om the shooter.

34

Table 9: The distribution of particles collected at ten feet away from the shooter after
one shot from a semiautomatic handgun.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
I shot particles with GSR
semiauto-
matic
Trial 1 0 2 0 0 34 O 2 34
10 it away
Trial 2 3 6 0 2 6 10 9 18
10 it away
Trial 3 0 0 .0 0 22 0 0 22
10 ft away
Trial 4 1 3 0 5 198 0 4 203
10 it away
Trial 5 1 l 0 0 1 0 2 1
10 ft away

 

 

 

 

 

 

 

 

 

Table 10: The distribution of particles collected at six feet away from the shooter after
one shot from a semiautomatic handgun.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
I shot Particles with GSR
semiauto-

matic

Trial 1 2 0 0 1 99 l 2 101
6 it away

Trial 2 2 6 0 2 31 0 8 33
6 ft away

Trial 3 2 4 0 2 82 0 6 84
6 it away

Trial 4 9 12 0 12 743 5 21 760
6 it away

Trial 5 9 1 0 2 53 0 10 55

6 ft away

 

 

 

 

 

 

 

 

 

35

 

 

Table 11: The distribution of particles collected at two feet away from the shooter after
one shot from a semiautomatic handgun.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
I shot Particles with GSR

semiauto-
matic
Trial 1 5 24 0 12 231 0 29 243

2 ft away
Trial 2 59 48 1 179 8665 1 107 8846

2 ft away
Trial 3 4 6 0 8 946 0 10 954

2 ft away
Trial 4 27 34 1 36 1461 7 61 1505

2 ft away
Trial 5 3 6 0 7 37 1 9 45

2 ft away

 

 

 

 

 

 

 

 

 

Table 12: Results of background particle collection prior to test fires involving one shot
from a semiautomatic handgun.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
I shot Particles with GSR
semiauto-
matic
Trial 1 0 O 0 0 0 1 0 1
background
Trial 2 0 0 0 0 0 2 0 2
background
Trial 3 0 O 0 0 0 0 0 0
background
Trial 4 3 O 0 1 0 0 3 1
background
Trial 5 0 0 0 O 0 1 0 1
background

 

 

 

 

 

 

 

 

 

36

 

 

One shot semiautomatic: distribution of unique GSR particles

 

 

 

120
100 . + 1 shot semiautomatic trial
1
30 , + 1 shot semiautomatic trial
E 2
1 E 60 . +1; shot semiautomatic trial ‘
o.
1 '3 3+ 1 shot semiautomatic trial ’ .
t E 40 - 1 4
g ‘ + 1 shot semiautomatic trial
= 20 .. ‘ 5
0 R
2R 6ft 10ft

distance from shooter

 

Figure 13: The distribution of unique GSR particles deposited at three distances from
the shooter after one shot from a semiautomatic handgun.

37

One shot semiautomatic: distribution of particles consistent with GSR

 

 

 

 

10000

9000. r.;.‘1’§1sf“sem"amo_h‘sumar
3000, 1 1 .1
E, 7000“ +lslntsemiautonntictrial
O .
‘E 6000- 1 2 . . . “
.3, +1shotserrnautorratrctnal
1's 5000- ‘1 3 1
E 4000* i+lshotserriautorraticuial'
S 3000- l 4 1‘
E 2000- ‘+lshotseniautormtictrial‘

1000- 1., _-5_ _ ___ __ w

0- -
2ft 6ft 10ft

Figure 14: The distribution of particles consistent with GSR deposited at three distances
from the shooter after one shot from a semiautomatic handgun.

A Comparison of the Results of One Shot from both a Semiautomatic Handgun and a

Revolver

A comparison of the numbers of GSR particles deposited after one shot from a
revolver and from a semiautomatic handgun appears in graph form in Figures 15 through
20. Overall, the numbers of both unique to and consistent with GSR particles deposited
were similar at all three distances from the shooter for both the semiautomatic and the

revolver. There was no significant difference between the number of particles deposited

38

at any of the three distances from the shooter when comparing the results obtained using

one shot from both firearms.

Number of unique GSR particles deposited 2 it away from the shooter
after one shot from a revolver and a semiautomatic handgun

120

 

number of particles

 

 

 

Figure 15: A comparison of the number of unique GSR particles collected at two feet
from the shooter after one shot was fired from a revolver and a semiautomatic handgun.

39

Number of unique GSR particles deposited 6 ft away from the shooter
after one shot from a revolver and a semiautomatic handgun

25

 

number of particles

 

 

 

Figure 16: A comparison of the number of unique GSR particles collected at six feet
from the shooter after one shot was frred from a revolver and a semiautomatic handgun.

40

Number of unique GSR particles deposited 10 It away from the shooter
after one shot from a revolver and a semiautomatic handgun

 

number 0? particles

 

 

 

 

 

Figure 17: A comparison of the number of unique GSR particles collected at ten feet
from the shooter after one shot was fired from a revolver and a semiautomatic handgun.

41

Number of particles consistent with GSR deposited 2 it away from the
shooter after one shot from a revolver and a semiautomatic handgun

10000
9000 ,.
8000.
7000-
6000--
50000:
4000.
3000-
20004.

 

number ’of particles

 

 

 

Figure 18: A comparison of the number of particles consistent with GSR collected at
two feet from the shooter after one shot from a revolver and a semiautomatic handgun.

42

Number of particles consistent with GSR deposited 6 It away from the
shooter after one shot from a revolver and a semiautomatic handgun

 

number of parficlos

 

 

 

Figure 19: A comparison of the number of particles consistent with GSR collected at six
feet from the shooter after one shot from a revolver and a semiautomatic handgun.

43

Number of particles consistent with GSR deposited 10 It away from the
shooter after one shot from a revolver and a semiautomatic

250

 

number of particles

 

 

 

 

Figure 20: A comparison of the number of particles consistent with GSR collected at ten
feet from the shooter after one shot from a revolver and a semiautomatic handgun.

Results of Test Fires Using Six Shots from a Semiautomatic Handgun

In trials involving six shots from a semiautomatic handgun, some data
extrapolations were made. The instrumentation used was designed to end the analysis
after ten thousand particles are analyzed. For some of the samples taken after six shots
from a semiautomatic, this threshold was reached after only a small portion of the search
area was examined. Throughout the analysis of the samples generated during this study it

was noted that the particle deposition was even throughout the stub surface. Assuming

this, the particle tabulations for stubs with greater than ten thousand particles were
extrapolated for the portion of the stub area not searched.

In test fires using six shots from a semiautomatic handgun, unique GSR particles
were found at all three distances from the shooter in all five trials. The number and
identity of the unique GSR particles that were collected are tabulated in Tables 13
through 16. The distribution of these particles was inconsistent. In three out of five
trials, the number of unique GSR particles deposited decreased as the distance from the
shooter increased. In the remaining two trials, more unique GSR particles were deposited
at ten feet from the shooter than at six feet away. In all trials, the highest number of
unique GSR particles was deposited at two feet from the shooter. A graph of these results
appears in Figure 21. In comparing the five trials, the number of unique GSR particles
deposited varied from 57 to 1878 at two feet away from the shooter, from 24 to 139 at six
feet away from the shooter, and from 8 to 127 at ten feet away from the shooter.

Particles consistent with GSR were deposited at all three distances from the
shooter in all five trials. The number and identity of these particles are tabulated in
Tables 13 through 16. The distribution of these particles was inconsistent. In three out of
the five trials, more particles consistent with GSR were deposited at ten feet than at six
feet. In the remaining two trials, the number of particles deposited decreased as the
distance from the shooter increased. In all trials, the highest number of particles
consistent with GSR was deposited at two feet from the shooter. A graph of these results
appears in Figure 22. In comparing the five trials, the number of particles consistent with
GSR deposited varied from 2,465 to 64,161 at two feet from the shooter, from 572 to

3163 at six feet fiom the shooter, and from 44 to 10,007 at ten feet from the shooter.

45

Table 13: The distribution of particles collected at ten feet from the shooter after six
shots from a semiautomatic handgun.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
6 shots particles with GSR
semiauto-
matic
Trial 1 6 2 O 4 49 0 8 53
10 it away
Trial 2 51 53 17 129 5506 19 104 5671
10 it away
Trial 3 1 9 0 13 30 1 10 44
10 ft away
Trial 4 76 51 3 108 9881 15 127 10007
10 it away
Trial 5 41 75 2 73 630 23 116 728
10 ft away

 

 

 

 

 

 

 

 

 

Table 14: The distribution of particles collected at six feet from the shooter after six
shots from a semiautomatic handgun.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
6 shots particles with GSR
semiauto-
matic
Trial 1 59 58 0 79 1603 0 117 1682
6 ft away
Trial 2 29 110 7 92 3026 27 139 3152
6 it away
Trial 3 6 18 0 36 988 6 24 1030
6 ft away
Trial 4 21 15 14 11 2835 3 36 2863
6 ft away
Trial 5 23 39 1 35 524 12 62 572

6 ft away

 

 

 

 

 

 

 

 

 

46

 

 

Table 15: The distribution of particles collected at two feet from the shooter after six
shots from a semiautomatic handgun.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
6 shots particles with GSR
semiauto-
matic
Trial 1 98 57 1 94 2362 8 155 2465
2 it away
Trial 2 520 1358 189 2459 61229 28 1878 64161
2 ft away 4
Trial 3 18 39 1 106 4868 12 57 4987
2 ft away
Trial 4 367 1050 105 1217 51844 27 1417 53444
2 it away 8
Trial 5 92 236 8 359 10426 85 328 10878
2 it away

 

 

 

 

 

 

 

 

 

Table 16: Results of background particle collection prior to test fires involving six shots

from a semiautomatic.

 

 

 

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
6 shots particles with GSR
semiauto-
matic
Trial 1 0 0 O 0 0 0 0 0
background
Trial 2 O 0 0 0 1 0 0 1
background
Trial 3 0 0 O 0 0 0 0 0
background
Trial 4 O 0 0 0 1 0 0 1
background
Trial 5 0 0 0 0 0 O O 0

background

 

 

 

 

 

 

 

 

 

47

 

 

6 shots semiautomatic: distribution of unique GSR particles

 

 

 

 

2000

1800 -
.o 1600 - __ _ , _g _____fl
E 1400 . +6shotssemiautormtictr'all
a 1200 . . . .
£- 10004 +6stntssemrautonntrctrra12
g 800 . +6shots semiautormtictr'nl3 _
is 600 J . . .
l: .
1 400 - +6shots semrautomatrctml4

200 - __,._ 6 shots semiautomatic trhlS

0 a; -- L, _. .fi__. _. W

 

 

2ft 6ft 10ft
distance from shooter

P...“ __ -__._

 

Figure21: The distribution of unique GSR particEsdEpo’sited at three distances 0001 the
shooter after six shots fi'om a semiautomatic handgun.

48

 

6 shots semiautomatic: distribution of particles consistent with

70000

GSR

 

60000 -
i 50000.-
40000 -
30000
20000 -
10000 -

0
—
ii
a
o.
“It
2
0
.n
E
:r
:1

l

 

0

X

gxg:

 

Y b!
2ft

6ft 10fi
distance from shooter

 

 

1+ 6 shots semiautomatic tr'ani
,_.,_ 6 shots semiautomatic trial 3'!
' _x_ 6 shots semiautormtic trial 4

1.5.. 6 shots semiautomatic tria151 t

Figure 22: The distribution of particles consistent with GSR deposited at three distances
from the shooter after six shots from a semiautomatic handgun.

A Comparison of the Results of One Shot and Six Shots from a Semiautomatic Handgun

A comparison of the numbers of GSR particles deposited after one shot and six

shots were fired using a semiautomatic handgun appears in graph form in Figures 23

through 28. The numbers of particles unique to GSR were generally higher after six shots

than after one shot. The number of particles consistent with GSR was higher after six

shots in most of the trials. However, in some of the trials, the numbers of particles

consistent with GSR after one and six shots are close at varying distances from the

shooter.

49

Number of unique GSR particles deposited 2 ft away from the
shooter: 1 shot vs. 6 shots from a semiautomatic handgun

2000 .
1750- -
1500

1250 .
1000 -
750 . -
500- _. _
250 . -. _, ._

 

number of pit-Tiers I

 

 

 

 

 

Figure 23: A comparison of the—number (If un—ique GS—RSp—articl’es deposited~ at two feet 4
from the shooter after firing one and six shots from a semiautomatic handgun.

50

Number of unique GSR particles deposited 6 ft away from the
shooter: 1 shot vs. 6 shots from a senriautonratic handgun

 

 

 

 

gh__— _ _ ____. __ . __ _

Figure 24: A comparison of the number of unique GSR particles-deposited at six feet—
from the shooter after firing one and six shots from a semiautomatic handgun.

 

 

51

 

number a parti

 

 

 

 

0:00}; is: Acomparison or the numbermofirnique GSR smitesEFposiisa—JQ téet "
from the shooter after firing one and six shots from a semiautomatic handgun.

52

Number of particles consistent with GSR deposited 2 ft away from
the shooter: 1 shot vs. 6 shots from a semiautomatic handgun

 

 

 

number of particle

 

 

 

Figure 26: A comparison 0f the number of particles consistent wiTh GSR deposfied at H
2 it away from the shooter after firing one and six shots from a semiautomatic handgun.

53

Number of particles consistent with GSR deposited 6 it away from
the shooter: 1 shot vs. six shots from a semiautomtic lumdgun

 

number of particle

 

 

 

FiguTe 27 A 601000650 of the nmnber of particles consistent wrth GSR deposited at I
6 ft away from the shooter after firing one and six shots from a semiautomatic handgun.

54

Number of particles consistent with GSR deposited 10 ft away from
the shooter: 1 shot vs. six shots from a semiautomatic handgun

 

number of particle

 

 

 

 

 

Figure 28* Azorhpar—ison of the number— of particles consistent with GSR deposited at
10 ft away from the shooter after firing one and six shots from a semiautomatic handgun.
A Comparison of the Results from Six Shots Fired Using a Revolver and a

Semiautomatic Handgun

A comparison of the number of GSR particles deposited after six shots were fired
using a revolver and a semiautomatic handgun appears in graph form in Figures 29
through 34. The results show that overall more GSR particles were deposited after
discharging the semiautomatic than were deposited after discharging the revolver.
However, in some of the trials, the numbers of GSR particles deposited are similar for the

two firearms at varying distances from the shooter.

55

Number of unique GSR particles deposited at 2 ft'from the shooter: 6
shots from a revolver vs. a semiautomatic

 

number of particle

 

 

 

 

Figure 29: A comparison of the numberof unique GSR particIes deposited atn2 fifrom
the shooter after firing six shots from a semiautomatic handgun and a revolver.

56

Number of unique GSR particles deposited at 6 ft from the shooter.
6 shots from a revolver vs. a semiautomatic

160

140 i _

120 -
100

 

number of particle '
W
O

 

 

 

 

 

Figure 30: A comparison of the number of unique GSR particles deposited at 6 ft fi'om
the shooter after firing six shots from a semiautomatic handgun and a revolver.

57

Fume" 351360013er pairfic—les it Tort awayt'rom the shooter:— 6 ’ 7
shots from a revolver vs. a semiautomatic

 

140
120 . .. - - -
100 - .

number of particl
O\
o

 

 

 

 

 

 

Figure 31: A comparison of the number of unique GSR particles deposited at 10 ft from
the shooter after firing six shots from a semiautomatic handgun and a revolver.

58

Number of particles consistent with GSR deposited at 2 ft from the
shooter: 6 shots from a revolver vs. a semiautomatic

 

if nunfber of particle

 

 

 

 

Egan-{35:}. comparison of the number ofparticIes consistent with ash ciepositedat 1’
2 ft fiom the shooter after firing six shots from a semiautomatic handgun and a revolver.

59

Number of particles consistent with GSR deposited at 6 ft from the
shooter: 6 shots from a revolver vs. a semiautomatic

 

I numberT 0f particle

 

 

 

 

 

 

Figure 33TA ngfisoJ of the anmbeFOf paT'ticIes consistent mmGSR_de—posifed at _ 7
6 ft from the shooter after firing six shots from a semiautomatic handgun and a revolver.

60

Number of particles cons'mtent with GSR deposited at 10 ft from the
shooter: 6 shots from a revolvervs. a semiautomatic

 

numBer of particle

 

 

 

 

Figure 34: A comparison of the numbers of particlesETrnsistent withvG-SRdepositedfiat
10 ft from the shooter after firing six shots fi'om a semiautomatic handgun and a revolver.

61

Chapter 4
SUMMARY AND CONCLUSIONS

This study was designed to assess the distribution of GSR when a firearm is
discharged indoors. The distance the GSR particles traveled from the gun as well as the
number of particles deposited was recorded. The number of shots fired and the type of
firearm used were varied in order to evaluate the impact of these factors on GSR
distribution.

The results showed that unique GSR particles deposited as far as ten feet away
from the shooter in 79 out of the 80 trials carried out. This result shows that it is possible
for an individual pick up unique GSR particles by coming into contact with objects up to
ten feet away from the shooter. In addition, if the collection discs are seen as individuals
standing in a room during a shooting, it is possible for GSR to deposit on individuals
standing up to ten feet away from the shooter. Further research should be done in order
to assess this implication more fully.

The results also showed that the distribution of GSR was inconsistent for both
firearms used, regardless of the number of shots fired. The highest number of particles
generally deposited at two feet from the shooter. However, at six and ten feet from the
shooter, the number of particles deposited did not always decrease as the distance from
the shooter increased. In many trials, more particles were deposited at ten feet than at six
feet. This outcome may be due to the positions of the collection stubs in the room. The

stub at the ten-foot distance was placed approximately one foot from the side wall of the

62

room. Air currents created by the discharging firearm combined with the confined space
of the room may have contributed to the high numbers of particles deposited at the ten-
foot distance. Overall, the results showed that the number of particles deposited did not
always relate to the distance from the shooter, especially when considering the numbers
of particles deposited at six and ten feet away.

In comparing the impact of the number of shots fired on particle deposition, the
following observations were made. For test fires involving the revolver, the number of
unique GSR particles deposited was higher after six shots than it was after one shot.
More particles consistent with GSR were deposited after six shots at six and ten feet away
from the shooter. However, similar numbers of particles consistent with GSR were
deposited at two feet from the shooter after both one and six shots. For test fires
involving the semiautomatic handgun, overall, more GSR particles were deposited after
six shots than after one shot. However, in some of the trials, at a given distance from the
shooter the number of particles deposited was similar for both one and six shots. These
results indicate that the number of GSR particles deposited does not always correlate to
the number of shots fired.

In comparing the impact of the type of firearm used on the deposition of GSR,
two observations were made. For trials in which one shot was fired, the number of
particles deposited was similar for the revolver and the semiautomatic. For the trials
involving the discharge of six shots, more particles were deposited after discharging the
semiautomatic handgun. The semiautomatic was expected to deposit more particles due
to the cartridge ejection to the right of the firearm. The second observation made was

that the particle distribution was inconsistent for both the semiautomatic and the revolver.

63

As was mentioned earlier, inconsistencies in GSR distribution may arise from both the
firearm and the ammunition used.

The inconsistencies in particle deposition throughout all of the trials carried out in
this study suggest that GSR distribution is of little use for individuals reconstructing a
shooting event. For example, determining where a shooter was positioned while
discharging a firearm by collecting GSR samples alone would not prove reliable when
these inconsistencies are considered. However, sampling areas for GSR where a shooting
was known to occur may aid in assessing the implications for GSR transfer to non-
shooters.

The results obtained in this study both agree and disagree with past studies on
GSR distribution. Many individuals have reported inconsistencies in GSR distribution
such as those observed in this experiment. Krishnan and Munhall both reported that the
amount of GSR deposited could vary from shot to shot even if the same ammunition type
is used. Variation in the ammunition used provides one explanation for this phenomenon
(Krishnan, 1977; Munhall, 1961). Munhall also suggested that inconsistencies in GSR
deposition could be blamed on the firearm itself. For example, firing pin blows may vary
in strength (1961). In addition, Krishnan and Basu stated that the amount of GSR
deposited does not always add up with the number of shots fired (Krishnan, 1977; Basu et
al., 1997). The results of this study support this theory as well.

The results of this study also disagree with past studies on GSR distribution. This
experiment demonstrated that GSR can deposit as far as ten feet away from a shooter
when a firearm is discharged indoors. The Aerospace Corporation reported that GSR can

travel as far as three feet away from the shooter, but not as far as ten feet away (1977).

64

The study performed here also demonstrated that the number of GSR particles deposited
was inconsistent, and that it is possible for higher numbers of particles to deposit at
further distances from the shooter than at closer collection points. In experiments done
by White and Gross, their results showed that the number of unique GSR particles
deposited decreased as the distance from the shooter increased (1987).

The results of this experiment have provided great insight into the how GSR
particles are distributed when a firearm is discharged indoors. It was hoped that the use
of negative controls, repeated trials, and thoroughly documented experimental conditions
would provide reliable experimental results that would be of great use to those dealing
with GSR evidence. It was also hoped that this study might create a model for how GSR
experiments are performed and documented in the future. GSR is considered an
important form of evidence and is used by many law enforcement agencies when they are
faced with firearms related crimes. Therefore, it is of vital importance that research on
GSR distribution continues so that the implications of GSR samples yielding positive

results can be more fully understood.

65

Chapter 5

SUGGESTIONS FOR FUTURE RESEARCH

There are several possibilities for future research in the area of GSR distribution.
In order to evaluate the impact of ammunition type on GSR distribution, this experiment
can be repeated using one firearm and varying the ammunition used. Using more
firearms can also expand upon this experiment. Another addition that can be made to this
study is the presence of individuals in the room during the time of shooting at varying
distances from the firearm. The hands of the individuals can then be sampled for GSR.

Other options for future research on GSR distribution include expanding the
sampling to distances farther than ten feet away from the shooter, sampling to all sides of
the shooter, and evaluating the impact of air currents on the distribution. There are many
aspects of GSR distribution that are in need of further research. This creates many

options for individuals desiring to conduct research in this area.

66

APPENDICES

APPENDIX A

MATERIALS USED IN THIS EXPERIMENT

Firearms Used:

0 Ruger .357 Blackhawk revolver

0 Smith and Wesson 9mm semiautomatic handgun

Ammunition Used:

0 Winchester Super X 38 sp. 110 gr. Silvertip® HP

0 Winchester Super X 9mm Luger 115 gr. Silvertip® HP

Specimen Collection Materials:

0 12mm double coated carbon conductive adhesive tabs

o 1/2” aluminum specimen mounts with slotted heads

0 plastic storage tubes designed to hold one aluminum specimen mount

Experimental Setup Materials:

0 Detroit Corporation Bullet Trap Box
0 200 square foot room

SEM/EDX Analysis Equipment:
0 Philips XL30 Scanning Electron Microscope combined with the Oxford ISIS 300 X-

ray analyzer
- RJ Lee Personal SEM

67

APPENDIX B

RESULTS OF SUBSTRATE CONTROL EXAMINATION

 

 

 

 

Sample Pb, Sb, Sb, Ba Pb, Ba Pb, Sb Pb Ba Unique Particles
name: Ba GSR consistent
substrate particles with GSR
control

Carbon 0 0 0 0 0 0 0 0
tape batch

#1

Carbon 0 0 0 O 0 0 0 0
tape batch

#2

 

 

 

 

 

 

 

 

 

Table 17: Results of substrate control samples collected for each batch of carbon tape

used in this experiment.

68

 

APPENDIX C

DIAGRAM OF ROOM WHERE EXPERIMENT PERFORMED

 

 

 

 

 

 

 

 

 

 

 

 

7, 10" Bullet Trap
12' 4”
t.“
to . . .
’1‘ ’I‘ 4‘
2s 63 100 H
7' 10" 3

‘7! 5|]

 

 

 

12| 4"

Figure 35: Diagram of room where test fires were performed, not to scale.

69

LITERATURE CITED

LITERATURE CITED

American Society for Testing and Materials. (1995). Standard Guide for Gunshot
Residue Analysis by Scanning Electron Microscopy/Energy Dispersive Spectroscopy.
The Annual Book of ASTM Methods vol. 03.06, Philadelphia: ASTM.

Basu, S. (1982). Formation of gunshot residues. Journal of Forensic Sciences, 21, 72-
91.

Basu, 8., Boone, C., Denio, D., Miazga, R. (1997). Fundamental studies of gunshot
residue deposition by glue-lift. Journal of Forensic Sciences, 42, 571-581.

Basu, S. & Ferris, S. (1980). A refined collection technique for the rapid search of

gunshot residue particles in the scanning electron microscope. Scanning Electron
Microscopy, I, 375-3 84.

Germani, M. (1991). Evaluation of instrumental parameters for automated scanning

electron microscopy/gunshot residue particle analysis. Journal of Forensic Sciences, 3_6,
331-342.

Krishnan, S., Gillespie, K., & Anderson, E.J. (1977). Rapid detection of firearm
discharge residues by atomic absorption and neutron activation analysis. Journal of
Forensic Sciences, 16, 215-217.

Krishnan, S. (1982). Detection of gunshot residue: present status. In R. Saferstein (ed.),
Forensic Science Handbook (pp. 572-591). Englewood Cliffs: Prentice Hall, 1982.

Matricardi, V. & Kilty, J. (1977). Detection of gunshot residue particles from the hands
of a shooter. Journal of Forensic Sciences, 22, 725-738.

Meng, H. & Caddy, B. (1997). Gunshot residue analysis—a review. Journal of
Forensic Sciences, 42, 553-570.

Renfro, W. & Jester, W. (1973). Collection and activation analysis of airborne GSR.
Journal of Radioanalytical Chemistry, 15, 79-85.

70

Seamster, A. et a1. (1976). Studies on the spatial distribution of firearm discharge
residues. Journal of Forensic Sciences, 21, 868-882.

Singer, R., Davis, D., & Houck, M. (1996). A survey of gunshot residue analysis
methods. Journal of Forensic Sciences, 41, 195-198.

Thornton, J. (1986). Close proximity gunshot residues. Journal of Forensic Sciences,
31, 756-757.

Thornton, J. (1994). The chemistry of death by gunshot. Analytica Chimica Acta, 288,
71-81.

White, R. & Gross, M. (1987). Deposition of Gunshot Residue at Various Distances
from Discharging Firearms [lecture]. Raleigh: Unpublished paper.

Wolten, G., Nesbitt, R., Calloway, A., Loper, G., & Jones, P. (1977). Final Report on
Particle Analysis for Gunshot Residue Detection [report]. Report No. ATR-77(7915)-3.
El Segundo: The Aerospace Corporation.

Wolten, G., Nesbitt, R., Calloway, A., Loper, G., & Jones, P. (1979). Particle analysis
for the detection of gunshot residue. 1: SEM/EDX characterization of hand deposits from
firing. Journal of Forensic Sciences, 24, 409-422.

Wolten, G., Nesbitt, R., Calloway, A., & Loper, G. (1979). Particle analysis for the
detection of gunshot residue. 11: Occupational and environmental particles. Journal of
Forensic Sciences, 24, 423-430.

Zeichner, A. & Levin, N. (1997). More on the uniqueness of gunshot residue particles.
Journal of Forensic Sciences, 42, 1027-1028.

71

GENERAL REFERENCES

GENERAL REFERENCES

Basu, S. (1985). The Mechanism of GSR Deposition and its Probing Characteristics to
Reconstruct Shootings [lecture]. 43rd Annual Meeting of the Electron Microscopy
Society of America, August 5-9.

Goleb, J. & Midkiff, C. Jr. (1975). Firearms discharge residue sample collection
techniques. Journal of Forensic Sciences, 20, 701-707.

Kilty, J. (1975). Activity after shooting and its effect on the retention of primer residue.
Journal of Forensic Sciences, 20, 219-230.

Midkiff, C. (1977). Detection of gunpowder/gunpowder residues. A state-of-the-art
review and recommendations for further research [report]. Prepared for the Committee
on new development and research, American Society of Crime Lab Directors.

Munhall, B. (1961). Fundamental ballistics pertaining to investigations involving
firearms. Journal of Forensic Sciences, 6, 215-217.

Nesbitt, R., Wessel, J ., & Jones, P. (1976). Detection of GSR by use of the SEM.
Journal of Forensic Sciences, 21, 595-610.

Schlesinger, et a1. (1970). Special Report on Gunshot Residue Measured by Neutron

Activation Analysis, Report No. GA-9829 [report]. 10 August, San Diego: Gulf General
Atomic, inc.

Wallace, J. (1990). Chemical aspects of firearms ammunitions. AFT E Journal, 22, 364-
389.

White, R. & Owens, A. (1987). Automation of GSR detection and analysis by
SEM/EDX. Journal of Forensic Sciences, 32, 1595-1603.

Wolten, G., Nesbitt, R., & Calloway, A. (1979). Particle analysis for the detection of
gunshot residue. 111: The case record. Journal of Forensic Sciences, 24, 864-869.

72

*lllllllllllllllllll'llllllllllll’llllll’ll"l