Determination of Gunshot
Residue at Different Distances
Using AA and ICP
By: Chris Lloyd and John Siller
Background Information
• The three main components of gunshot
residue are Antimony (Sb), Lead (Pb), and
Barium (Ba)
• When the is gun fired, the gunpowder ignites
and the gases that are created propel the
bullet out of the barrel
• The gases propelled from the gun are burnt
and unfired gunpowder that contain metals
that can be detected
Purpose and Method
• Purpose- To determine the amount of
gunshot residue present on a t-shirt at
different distances using different calibers
• Method- We used the AA and ICP to analyze
the t-shirt samples and determine the amount
of Barium, Lead, and Antimony on each
sample
What We Did
• Shot 6 different guns with different calibers at 4 distances at
100% cotton t-shirts
• Variables
– Three Rifle Calibers
• 308
• 223
• 7.62 x 39 (AK)
– Three Handgun Calibers
• 45
• 9mm
• 38 Special
– Distances
•
•
•
•
Point Blank
1 foot
3 feet
5 feet
More of What We Did
• We cut each sample into four quadrants
• Soaked each sample in 0.2M nitric acid for at least an
hour and a half but most samples soaked for a
couple of days
• Vacuum filtrated every sample
to remove the t-shirts and
possible clumps of gunshot
residue
Original Plan
• Run quadrant I on the AA with three
different lamps
• Run quadrants II, III, and IV on the ICP
• Add concentrations of all four quadrants
together to get the amount of gunshot
residue on each sample
Atomic Absorption
• Used the Barium, Lead, and Antimony
hallow cathode lamps
• Ran quadrants I and II through the AA
• Standards were 1ppm, 3ppm, 7ppm,and
10ppm for the first quadrant
• 0.1ppm, 0.5ppm, 1ppm, 5ppm, and
10ppm for the second quadrant
Inductively Coupled Plasma
• Used 0.5ppm, 1ppm, 5ppm, and 10ppm
standards
• Only ran quadrant II
Data for Quadrant 1 on AA
AA
Quadrant 1
Gun/distance
Scan 1
9mm PB
1.205
9mm 1 ft
1.255
9mm 3 ft
3.596
9mm 5 ft
4.168
38 PB
1.659
38 1 ft
4.403
38 3 ft
4.653
38 5 ft
1.881
45 PB
2.347
45 1 ft
2.573
45 3 ft
4.91
45 5 ft
5.005
AK PB
3.006
AK 1 ft
Lost
AK 3 ft
3.409
AK 5 ft
Lost
223 PB
6.59
223 1 ft
6.805
223 3 ft
6.864
223 5 ft
6.924
308 PB
2.919
308 1 ft
Lost
308 3 ft
Lost
308 5 ft
Lost
Barium
Scan 2
1.291
1.4
3.676
4.107
1.643
4.448
4.771
1.9
2.524
2.572
4.899
5.132
3.043
Lost
3.404
Lost
6.58
6.735
6.846
6.927
2.926
Lost
Lost
Lost
Scan 3
1.247
1.438
3.774
4.082
1.733
4.586
4.786
1.957
2.519
2.656
4.973
5.16
3.099
Lost
3.442
Lost
6.536
6.714
6.759
6.976
2.838
Lost
Lost
Lost
Mean
1.248
1.365
3.682
4.119
1.678
4.479
4.737
1.912
2.463
2.6
4.927
5.099
3.049
Lost
3.419
Lost
6.569
6.751
6.823
6.942
2.895
Lost
Lost
Lost
Scan 1
2.517
4.133
0.567
0.557
5.759
2.729
1.334
0.557
3.067
1.513
0.735
0.47
4.732
13.84
2.376
0.784
2.003
2.35
0.269
0.488
1.631
4.28
1.027
0.642
Lead
Scan 2
2.504
4.191
0.584
0.553
5.764
2.849
1.32
0.558
3.048
1.535
0.707
0.443
4.691
13.67
2.356
0.765
2.004
2.383
0.282
0.483
1.643
4.287
1.007
0.561
Scan 3
2.507
4.13
0.536
0.568
5.768
2.824
1.303
0.57
3.11
1.483
0.736
0.47
4.707
13.61
2.299
0.785
1.928
2.364
0.279
0.48
1.645
4.306
0.988
0.58
Mean
2.509
4.151
0.562
0.559
5.763
2.801
1.319
0.562
3.075
1.51
0.726
0.461
4.71
13.7
2.344
0.778
1.979
2.366
0.277
0.484
1.64
4.291
1.007
0.595
Scan 1
0.332
0.184
0.145
0.149
0.162
0.18
0.177
0.139
0.277
0.214
0.144
0.141
0.157
0.349
0.204
0.152
0.198
0.197
0.166
0.181
0.194
0.263
0.179
0.151
Antimony
Scan 2 Scan 3
0.332 0.346
0.198 0.186
0.151 0.144
0.143 0.137
0.176 0.151
0.188 0.173
0.167 0.169
0.148 0.128
0.258 0.276
0.173
0.19
0.163 0.168
0.138 0.118
0.19
0.174
0.339 0.346
0.189 0.169
0.2
0.187
0.188 0.171
0.208 0.204
0.134 0.175
0.167 0.162
0.197 0.205
0.242 0.241
0.148 0.173
0.149 0.172
Mean
0.337
0.189
0.147
0.143
0.163
0.18
0.171
0.139
0.27
0.192
0.158
0.132
0.174
0.344
0.187
0.18
0.186
0.203
0.159
0.17
0.199
0.249
0.167
0.158
Handguns Quadrant 1 on AA
Rifles Quadrant 1 on AA
Handguns Quadrant 2 on AA
Rifles Quadrant 2 on AA
Handguns Quadrant 2 on ICP
Rifles Quadrant 2 on ICP
Comparison of Calibers on AA
Errors
• Both instruments had difficulty reading
our standards
• ICP couldn’t even detect our 0.1ppm we
originally made
• Uneven spread of gunshot residue on
the t-shirt samples
• Wrong method was picked for Lead and
Antimony on quadrant II for the AA
Set Backs
• Time
– We were only able to run quadrants I and II
• Availability
– Other labs groups had to use the same
instruments as us
• Instrumentation problems
– ICP torch was too dirty and couldn’t create a
strong enough plasma on our second to last day
of research so we had to use the AA
Conclusion
• Antimony was barely detectable in every
caliber and every distance
• Lead was usually the highest concentration
• 1 foot seems to have the most amount of all
the metals on it for both quadrants
• With so many variables it is hard to come to a
definitive conclusion
Future Work
• Measure GSR on entire shirt
• Increase the number of distances
• Implement the use of X-Ray
Fluorescence
• Study other calibers and ammunitions
including lead free bullets
Special Thanks
• Freedom Armory for providing the
weapons and ammunition as well as the
use of their shooting range
• Dr. Foy and Mrs. Mowery for helping us
to be reimbursed for doing something
as fun as shooting guns
• Matt Cunningham for providing the
method for preparing our samples