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 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

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