GUNSHOT RESIDUE

As investigators, you should know that a “Gunshot Residue Test” – or “GSR” – is not a surefire exam to determine whether or not someone has fired a gun! In fact, it should be stressed that, according to Marc S. Taylor, a gunshot-residue expert from California who has testified nationally for both prosecutors and defense attorneys, a gunshot residue test “should never be referred to as showing that someone fired a gun”. The reason for this is the ability to contaminate – in both a contamination to show a “positive”, as well as to show a “negative” – that should cast all doubt on any validity of this exam. Why, then, is the test conducted? Perhaps because it looks good when people watch it being done on TV, on shows like CSI!
It has been noted that across the country defense experts are fighting the validity of “positive” results, as tests have proven a “false-positive” could occur from contaminants from items that already have gunshot residue on them – such as handcuffs, car seats, or even the police officers clothing. This is combined with the known “negative” results which could easily be obtained from having cleaned ones hands before a swab being taken. It has long been considered an unreliable test any time the subject was out of view of the tester or police officer for any amount of time, as one could easily wipe and clean hands, thus removing particles before being swabbed.

WHAT IS GUNSHOT RESIDUE?
The tiny particles that are released when a handgun is fired, consisting of lead, barium and antimony particles. In theory, when firing a gun, these particles are displaced into the air and onto the hands of the person firing the gun – thus, testing “positive” for these elements, one would – TRY – to conclude that you fired the gun. However, as noted above, there are variables which cannot be controlled that could easily cause a “false positive” – as well as a “false negative” – that should leave any investigator with the very big question that needs to be answered any time such a test is recommended – “Why Should A Gunshot Residue Test be Conducted?”

GUNSHOT RESIDUE TEST FOR SUICIDES

One investigation where it could be considered more valuable than others may be in the investigation of apparent self-inflicted gunshot wounds.
Provided there was no opportunity for contamination.
The examination of gunshot residue can disprove an assumption made falsely or mistakenly. For example, in the case of an apparent suicide involving a handgun, a gunshot residue collection should be done on the hands of the deceased. If no residue is found, the case could actually be a murder made to look like a suicide.
Certainly a consideration for the investigator.