How does gunshot residue work

It is therefore essential that every possible means of preventing cross contamination be implemented. Don Penven has more than 35 years direct and indirect experience in law enforcement. He currently serves as a technical support representative and technical writer for Sirchie Finger Print Labs. He maintains the Blog: www.

Printer Friendly Page. Compiled by Don Penven Gun Shot Residue, or simply GSR, is a means of testing for the presence of certain materials on the hands and clothing of a subject in hopes of determining that this individual may have discharged a firearm. The Chemistry of Gunpowder Most historians agree that the ancient Chinese discovered what we refer to as gunpowder. What is GSR? Primer Residue When a gun is fired, the gunshot residue particles - small particles produced during the gunpowder explosions - are emitted from the back of the weapon and the muzzle.

GSR Particle More than 30 years ago scientists working in crime laboratories developed a different means of analyzing gunpowder residue. Get it during the discovery stage. Is the count 20 or less? An individual can get that by coming in contact with the police or other people. Demand a breakdown of the residue. If all three elements are not included, it may not be GSR.

Please turn on JavaScript and try again. Forensic Science Services. Expand All Collapse All. Page Content. Spanish Hmong Somali. Forensic Testing Services. Drug Chemistry. Questioned Documents. Latent Prints. Only particles from the primer are considered to be characteristic of GSR. Particles from the bullet, cartridge case and barrel are either indicative or commonly associated with, but on their own are not exclusive to, GSR. Forensic analysis involves the careful recovery of the microscopic metallic particles from clothing, surfaces or directly from the skin or hair of an individual.

The samples are coated with a thin layer of carbon and then examined for their characteristic elemental composition and morphology using a powerful scanning electron microscope SEM. However, even if a GSR test comes back positive, there are numerous issues that can impact the strength and reliability of such evidence.

First, in every GSR test report — whether the test comes back positive or negative for GSR — there is always a disclaimer. A positive GSR test result does not necessarily mean that a defendant has fired a gun. Even if the fused particles of barium, antimony, and lead are found, they could have come from other materials, such as brake pads or fireworks, or they could be a result of a contaminated sample.

Similarly, a negative GSR test result does not necessarily mean that a defendant has not fired a gun. The GSR particles could have been washed away or the Defendant could have been wearing gloves.