What is Gun Shot Residue?
Gunshot residue (GSR) is an important trace evidence that assists forensic scientists in solving a wide range of firearm-related incidents.
It is comprised of unburned or partially burned gunpowder particles, soot, nitrates, and nitrites from powder combustion, primer particles of heavy metals such as lead, barium, and antimony, and bullet or bullet jacket particles that are vaporised when a firearm is discharged. (Rowe, 2000).
The identification of the shooter, as well as bullet identification from a gunshot wound, aid in the reconstruction of a crime scene.
What are the components of Gun Shot Residue?
Understanding the chemistry of ammunition is essential for GSR testing. Primer and gunpowder are made up of specific chemical ingredients in specific amounts. Lead, barium, or antimony are the main components of primer; frequently, all three are present. Nitrocellulose, a highly combustible chemical, is the basic constituent in many varieties of modern gunpowder. Other formulas include nitrocellulose and up to 40% nitroglycerine, as well as up to twenty other chemical compounds.
How to collect GSR Sample?
GSR evidence is only present when a handgun is used; when a bullet leaves a rifle or pellets leave a shotgun, the residue is left inside the barrel. As a result, while on the scene, investigators collect as many samples as possible for future testing.
Law enforcement personnel can collect samples from the skin and clothing of anyone they suspect were involved in the incident. GSR evidence can be lost or destroyed if evidence related to the incident is not properly kept. Washing one’s hands or clothing may remove Gun shot residue easily.
Evidence should be collected carefully and to ensure that evidence can be presented in court, police officers, detectives, and crime scene investigators take the following steps:
1.Put on a pair of latex gloves or wash your hands.
2. Soak two cotton swabs in dilute (5 percent) nitric acid and thoroughly swab the suspect’s back and front of right hand, back and front of Left hand should be swabbed throughly with 5% dil. HNO3
3. Swabs should be pack in a plastic bag and labeled with initials of collecter with the date, and the exhibit number.
4. Swab both the right and left cheeks of the face if the use of a rifle or shotgun is suspected.
5. If you have a spent casing, swab the interior with plain water (no acid), place the swab in a plastic bag, and label the bag “casing.”
6. Pack items of clothing to be tested for gunshot residue in separate plastic bags.
How long does the residue of gunpowder remain?
Typically, GSR particles only lasts 4–8 hours on the hands of a living human. It’s particles can be eliminated from the hands over time through contact with other objects. Washing or wiping the hands on anything, even putting them in and out of pockets, can transfer gunshot residue.
Instrument for Gun Shot Residue Analysis
“Scanning electron microscopy with energy dispersive analysis” (SEM-EDA) is one of the most effective procedures for testing GSR. To undertake detailed surface examination and high magnification viewing of extremely small features, the technician use a scanning electron microscope and an energy dispersive X-ray spectrometer.
Read More about GSR Analysis here: Gun Shot Residue