What is Gunshot Residue?

Summary

The video explains the process of gunshot residue (GSR) analysis in crime investigations. When a firearm is discharged, tiny particles of burnt gunpowder, lead, and metal are released and can cling to nearby surfaces. Detecting GSR on individuals can help investigators determine proximity to a gunshot. The analysis involves swabbing surfaces and examining the particles using advanced microscopy techniques. However, GSR evidence has limitations, as it can be transferred indirectly or washed off, and the presence of GSR doesn't always confirm someone fired a gun.

Takeaways

• 💥 Gunshot residue (GSR) consists of burnt and unburnt gunpowder, vaporized lead, and fragments of metal from the cartridge.
• 🔬 These particles cling to surfaces close to the firearm, typically within 3 to 5 feet from the gun’s muzzle.
• 🤚 Factors such as the shooter's stance, handedness, and weapon handling can affect the amount of GSR deposited on them.
• 🧪 A GSR test kit uses sterilized adhesive tabs to swab hands, surfaces, or clothing for microscopic metallic particles.
• 🖥️ The sample is analyzed using scanning electron microscopy and energy dispersive x-ray analysis, looking for antimony, lead, and barium.
• ⏳ GSR tests should be done within six hours after the incident, and subjects should not wash their hands beforehand.
• 🛡️ Police may bag the hands of a deceased person to prevent contamination before performing a GSR test.
• 🔄 GSR can undergo secondary or tertiary transfer, and contamination in environments like police stations is a known issue.
• 🤔 Testing positive for GSR could mean someone fired a gun, was near a gunshot, or came into contact with someone who fired a gun.
• ⚖️ GSR evidence is admissible in court but has limitations due to potential contamination, secondary transfer, and the common presence of GSR elements in non-firearm-related materials like fireworks or brake pads.

Q & A

What is gunshot residue (GSR) composed of?

Gunshot residue (GSR) consists of microscopic particles of burnt and unburnt gunpowder, vaporized lead, and tiny fragments of metal from the cartridge casing.

How far can gunshot residue particles typically travel?

The fine cloud of particles from gunshot residue usually doesn't travel further than three to five feet from the muzzle of the gun.

What factors can affect the amount of GSR deposited on a shooter?

The amount of GSR deposited can be influenced by the shooter's handedness, stance, and how they handle the weapon.

Why do police use sterilized adhesive tabs in GSR tests?

Sterilized adhesive tabs are used in GSR tests to swab the person's hands, clothing, or surfaces for microscopic metallic particles, ensuring accurate and uncontaminated sample collection.

What elements are experts looking for in a GSR test?

Experts look for the presence of antimony, lead, and barium in gunshot residue tests.

Why is it important to perform a GSR test within six hours of the suspected incident?

It is crucial to perform the test within six hours because the particles can be easily removed or contaminated by activities, including washing hands, making it harder to detect the original GSR.

What precautions do police take at a potential homicide scene to preserve GSR evidence?

Police often place the hands of the deceased in paper bags to prevent transfer or contamination of potential GSR evidence for later testing.

Can gunshot residue undergo secondary or tertiary transfer, and how can this affect investigations?

Yes, GSR can undergo secondary or tertiary transfer, which can lead to contamination in places like interview rooms, potentially complicating investigations.

What does a positive GSR test indicate, and why is it not conclusive evidence of firing a gun?

A positive GSR test may indicate that an individual recently fired a firearm, was in close proximity to a gun being fired, or had contact with someone who fired a gun. However, the presence of GSR is not conclusive proof since the elements found in GSR can also be present in other materials, such as brake pads or fireworks.

How is the concentration of particles within a GSR sample used to assess its origin?

If there are only a few particles in the sample, it might suggest they were not from the discharge of a firearm. However, if there are over 2,000 relevant particles, it's harder to argue that they came from other sources.