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GSR

GSR. Gun shot residue. Gun Shot Residue. Trace evidence may be found after a gun has been fired. During this combustion reaction, not all of the material is fully used. The excess material may be expelled from the barrel, casing, or wherever the smoke and heat escape.

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GSR

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  1. GSR Gun shot residue

  2. Gun Shot Residue • Trace evidence may be found after a gun has been fired. • During this combustion reaction, not all of the material is fully used. • The excess material may be expelled from the barrel, casing, or wherever the smoke and heat escape. • The material may settle on the shooters hands, clothing or hair and be found at the scene as well.

  3. GSR • Chemicals are used to react with compounds left by the ignition of the gun powder • Gun powder is made of nitrates • Metals (lead and barium) from the primer may also be present • These chemicals are what make Gun Shot Residue (GSR)

  4. GSR • You will be using two different chemicals that react with the presence of the products of a fired weapon. • Diphenylamine detects the presence of nitrates • Sodium rhodizonatedetects the presence of lead and barium

  5. What you will do • You will test GSR with the two chemicals • You will run a positive control using lead nitrate • You will then test the unknown for GSR

  6. The scenario Two individuals were apprehended for the robbery of a convenience store. The store clerk was shot in the torso and later died at the hospital.

  7. No gun was found at the scene and neither individual is taking the blame for firing the gun.

  8. A piece of sleeve, around the wrist area, from each individual’s shirt has been sent to you. Your job is to help authorities determine if either had anything to do with the shooting.

  9. What to do • Get a piece of notebook paper to record your findings. You will be able to use this paper on your ballistics test. • Your paper should include what makes up GSR and what chemicals are used to detect these chemicals. • You will also include the colors of a positive and negative result using these chemicals.

  10. Make a chart showing the results of everything you do. • Label everything clearly so you understand the results of all your tests. • You will first do a positive control test on an alcohol pad using lead nitrate.

  11. Gun residue presumptive test • Open the alcohol pad and put into a petri dish. Place a drop of lead nitrate on two corners of the alcohol swab • Place a drop of Diphenylamine on the drop of the lead nitrate. Note that this chemical detects the presence of nitrates from the gun powder • Place a drop of sodium rhodizonateon the other drop of the lead nitrate. Note that this chemical detects the presence of lead and bariumfrom the primer. • Record color changes occurring with each chemical.

  12. Expected results

  13. GSR test on the suspects • Now you will test the presence of GSR on the sleeves of the suspects. • The suspects are identified as suspect 1 and suspect 2. • Obtain a sample of each of one of the suspects sleeves. DO NOT TOUCH WITH YOUR HANDS. USE A CLEAN FORCEP. • Add a drop of each of the test chemicals (Diphenylamine and sodium rhodizonate) and record your results. • Repeat with the other suspect.

  14. Expected results

  15. Your conclusion Remember, neither individual is taking the blame for firing the gun. Are they telling the truth?? Write your conclusion on your paper.

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