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 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 AAQuadrant 1BariumLeadAntimony Gun/distanceScan 1Scan 2Scan 3MeanScan 1Scan 2Scan 3MeanScan 1Scan 2Scan 3Mean 9mm PB mm 1 ft mm 3 ft mm 5 ft PB ft ft ft PB ft ft ft AK PB AK 1 ftLost AK 3 ft AK 5 ftLost PB ft ft ft PB ftLost ftLost ftLost

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Errors Both instruments had difficulty reading our standards ICP couldn’t even detect our 0.1ppm we originally made Uneven spread of gunshot residue on the t-shirt samples Wrong method was picked for Lead and Antimony on quadrant II for the AA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