Wednesday, May 20, 2015

Gunshot Residue (GSR) and Testing

What is GSR and the collection process?

GSR, an acronym for Gunshot Residue, is deposited — or not — on the hands and clothes, or any other objects, of someone or something in the vicinity of a discharged firearm. Special sealed containers with tabs bearing an adhesive substance are used to collect microscopic particles — hands and face, as well as other areas of concern (i.e. clothing); there is one tab that remains sealed and unused as a control for the laboratory.

What is tested for?

The components are lead, antimony and barium. These are in the primer of the cartridge, and not the gunpowder of the cartridge itself. The discharge creates a specific burned component of these three chemicals that is unique to cartridge primers — although similar to fireworks, not the same microscopically. The hope of GSR testing is that the GSR will tell who discharged the firearm and who was the victim. The answer being sought is simply positive or negative for GSR — who is the shooter and who is the victim?

Common Scenarios

The two scenarios that are most often asked about are:

1. Post Incident

Positive results can be circumstantial and will only indicate the individual may have discharged a firearm, may have been in the vicinity of a firearm that was discharged, or may have come in contact with an item with gunshot residue on it. Similarly, negative findings will not preclude the above and that one or more of the persons discharged a firearm.

2. Post Exhumation

Upon completion of the autopsy the body is cleaned for transport to the funeral home. At the funeral home the body is cleansed thoroughly and prepped as directed for burial. If there is an open casket or private viewing, the body is often prepared with makeup in those areas that would be exposed. This prevents any reliable GSR testing.

The Best Course of Action

It is best to review all the available records, reports and photographs to determine, as best possible, the most accurate conclusions based upon the direct and circumstantial evidence. GSR, like all evidence, is direct evidence that is subordinate and subjective to related circumstantial evidence. You must ask the who, what, when, where, why and how of all evidence and how they interrelate.

Brian Blackwell Investigations | Seattle, WA