Determination of Gunshot Residue at Different Distances Using AA and ICP

1. Determination of Gunshot Residue at Different Distances Using AA and ICP By: Chris Lloyd and John Siller

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. Inductively Coupled Plasma • Used 0.5ppm, 1ppm, 5ppm, and 10ppm standards • Only ran quadrant II

9. Data for Quadrant 1 on AA

10. Handguns Quadrant 1 on AA

11. Rifles Quadrant 1 on AA

12. Handguns Quadrant 2 on AA

13. Rifles Quadrant 2 on AA

14. Handguns Quadrant 2 on ICP

15. Rifles Quadrant 2 on ICP

16. Comparison of Calibers on AA

17. Errors • Both instruments had difficulty reading our standards • ICP couldn’t even detect our 0.1ppm we originally made • Uneven spread of gunshot residue on the t-shirt samples • Wrong method was picked for Lead and Antimony on quadrant II for the AA

18. 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

19. 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

20. 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

21. 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