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 as directed in the kit—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 (a common belief). 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.
It is our experience that GSR will not further the quest for answers. There are only two possibilities to GSR testing, per tab collected and tested: positive and negative. If positive, it only confirms a person being in the vicinity of the discharge, not that they did or did not shoot. Similarly, if negative it is not conclusive they were not in the vicinity of or discharged a firearm. In addition, there is a possibility that the movement of the bodies may have spoliated that evidence. As this is microscopic and multiple areas are collected from, this is a variable that we cannot specifically address. Most requests for GSR involve multiple persons—such as a homicide/suicide or suicide/suicide seen in domestic violence or end of life decisions of terminally elder people. The hope is that the GSR will tell who discharged the firearm and who was victim to the discharge without doing so themselves. The answer being sought is simply positive or negative for GSR, which gives four unspecified possibilities (alleged shooter and alleged victim):
Generally, we do not rely on GSR to either support or refute a person being involved in the discharge of a firearm. Instead we rely on other available information, facts and evidence.
- Positive and positive
- Positive and negative
- Negative and positive
- Negative and negative
Common ScenariosThe two scenarios are most often asked about are:
1. Post IncidentPositive results are circumstantial and will only indicate these individuals may have discharged a firearm, may have been in the vicinity of a firearm and 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 ExhumationUpon 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.
What does this tell us about GSR?The only forensic conclusions are:
- The presence of GSR is that the object in question was in the vicinity of a firearm discharge at a time the GSR cannot determine; and
- The absence of GSR is that the object in question may or may not have been in the vicinity of a firearm discharge. These findings do not include that GSR can be wiped or washed off, it cannot be determined how long it has been present, and no other reliable conclusions can be drawn.