Gunshot Residue Analysis

Question 1

What do you put into a gun?

Answer 1

Cartridges (also known as rounds),which contain the bullets

Question 2

What are the cartridge components?

Answer 2

Case, bullet, powder, primer

Question 3

What is the primer composed of?

Answer 3

• Lead styphnate (a shock sensitive explosive)
• Barium nitrate (oxidizer)
• Antimony sulfide (fuel)

Question 4

What happens then the trigger is pulled?

Answer 4

• Firing pin strikes the primer cup
• Primer is crushed, detonates
• Energy from primer sets off gunpowder
• Things go boom
• The hear causes the primer to vaporize
• Particles re-solidify quickly, deposit on shooter and nearby objects and people

Question 5

What is GSR?

Answer 5

• Particles that contain all three elements; lead barium and antimony
• Typically spherical about 1-10 um in diameter

Question 6

Why is GRS is a misnomer?

Answer 6

We are actually looking for residue of the primer

Question 7

What does the GSR kit contain?

Answer 7

Instructions, questionnaire, gloves, 2 CFS seals, and 2 pairs of sampling stubs. 4 stubs are collected per suspect, 2 per hand, web and back of hand. (Officer who takes samples, cant have used a gun that day and must wash hands before)

Question 8

How is GSR detected?

Answer 8

• Scanning electron microscopy- energy dispersive x-ray analysis (SEM/ EDX)
• Automated analysis
• 24-48 hours to run handkit
• Instrument flags particle, but they need to be confirmed by a person

Question 9

What do positive results mean?

Answer 9

Rired a gun, was near the gun when it fired, touched a surface with GSR on it, for example a cartridge case, or a gun from a crime scene or contamination from police office

Question 10

What does negative results mean?

Answer 10

Didn’t fire gun, gun didn’t deposit GSR on the hands, GSR was lost due to activity, and sampling was ineffective. Half-life of GSR is one hour. 8 hour is max, washing hands could lose from hands

Question 11

What are 3 limitations with GSR?

Answer 11

• Cant be used for firing angle, distance determination, or to associate a specific gun or ammunition
• Total number of GSR particles found can vary greatly
• Victims are not sampled because they are expected to have gunshot residue on them already

Question 12

What are two things that could resemble GSR?

Answer 12

Fireworks (pyrotechnic devices) and Airbags

Question 13

How do fireworks resemble GSR?

Answer 13

May generate particles similar in size range and composition to GSR

Question 14

How do airbags resemble GSR?

Answer 14

Some airbags use a primer similar to that used in ammunition

Question 15

T or F

Lack of GSR does NOT mean subject did not fire gun

Answer 15

True

Question 16

What range can GSR go?

Answer 16

Highest concentration at 45 feet, could go out to 60 feet

Question 17

What are 3 types of glass?

Answer 17

1. Flat glass- automotive
2. Container
3. Miscellaneous- optical lenses for cameras, decorative

Question 18

What is the forensic significance of glass?

Answer 18

• Types of fracture, direction of impact, sequence of impacts
• Hit and run and break and entering (2 types)

Question 19

T or F

Larger pieces of glass will be lost over time faster than smaller pieces?

Answer 19

True nigga bitch

Question 20

What does GRIM stand for and what it is?

Answer 20

Glass Refractive Index Measurement, Automated oil-immersion method