Determination of Gunshot Residue at Different Distances Using AA and ICP
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Determination of Gunshot Residue at Different Distances
Using AA and ICP
By: Chris Lloyd and John Siller
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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
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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
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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
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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
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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
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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
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Inductively Coupled Plasma
• Used 0.5ppm, 1ppm, 5ppm, and 10ppm standards
• Only ran quadrant II
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Data for Quadrant 1 on AAAA Quadrant 1 Barium Lead AntimonyGun/distance Scan 1 Scan 2 Scan 3 Mean Scan 1 Scan 2 Scan 3 Mean Scan 1 Scan 2 Scan 3 Mean9mm PB 1.205 1.291 1.247 1.248 2.517 2.504 2.507 2.509 0.332 0.332 0.346 0.3379mm 1 ft 1.255 1.4 1.438 1.365 4.133 4.191 4.13 4.151 0.184 0.198 0.186 0.1899mm 3 ft 3.596 3.676 3.774 3.682 0.567 0.584 0.536 0.562 0.145 0.151 0.144 0.1479mm 5 ft 4.168 4.107 4.082 4.119 0.557 0.553 0.568 0.559 0.149 0.143 0.137 0.14338 PB 1.659 1.643 1.733 1.678 5.759 5.764 5.768 5.763 0.162 0.176 0.151 0.16338 1 ft 4.403 4.448 4.586 4.479 2.729 2.849 2.824 2.801 0.18 0.188 0.173 0.1838 3 ft 4.653 4.771 4.786 4.737 1.334 1.32 1.303 1.319 0.177 0.167 0.169 0.17138 5 ft 1.881 1.9 1.957 1.912 0.557 0.558 0.57 0.562 0.139 0.148 0.128 0.13945 PB 2.347 2.524 2.519 2.463 3.067 3.048 3.11 3.075 0.277 0.258 0.276 0.2745 1 ft 2.573 2.572 2.656 2.6 1.513 1.535 1.483 1.51 0.214 0.173 0.19 0.19245 3 ft 4.91 4.899 4.973 4.927 0.735 0.707 0.736 0.726 0.144 0.163 0.168 0.15845 5 ft 5.005 5.132 5.16 5.099 0.47 0.443 0.47 0.461 0.141 0.138 0.118 0.132AK PB 3.006 3.043 3.099 3.049 4.732 4.691 4.707 4.71 0.157 0.19 0.174 0.174AK 1 ft Lost Lost Lost Lost 13.84 13.67 13.61 13.7 0.349 0.339 0.346 0.344AK 3 ft 3.409 3.404 3.442 3.419 2.376 2.356 2.299 2.344 0.204 0.189 0.169 0.187AK 5 ft Lost Lost Lost Lost 0.784 0.765 0.785 0.778 0.152 0.2 0.187 0.18223 PB 6.59 6.58 6.536 6.569 2.003 2.004 1.928 1.979 0.198 0.188 0.171 0.186223 1 ft 6.805 6.735 6.714 6.751 2.35 2.383 2.364 2.366 0.197 0.208 0.204 0.203223 3 ft 6.864 6.846 6.759 6.823 0.269 0.282 0.279 0.277 0.166 0.134 0.175 0.159223 5 ft 6.924 6.927 6.976 6.942 0.488 0.483 0.48 0.484 0.181 0.167 0.162 0.17308 PB 2.919 2.926 2.838 2.895 1.631 1.643 1.645 1.64 0.194 0.197 0.205 0.199308 1 ft Lost Lost Lost Lost 4.28 4.287 4.306 4.291 0.263 0.242 0.241 0.249308 3 ft Lost Lost Lost Lost 1.027 1.007 0.988 1.007 0.179 0.148 0.173 0.167308 5 ft Lost Lost Lost Lost 0.642 0.561 0.58 0.595 0.151 0.149 0.172 0.158
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Handguns Quadrant 1 on AA
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Rifles Quadrant 1 on AA
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Handguns Quadrant 2 on AA
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Rifles Quadrant 2 on AA
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Handguns Quadrant 2 on ICP
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Rifles Quadrant 2 on ICP
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Comparison of Calibers on AA
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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
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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
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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
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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
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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