Crime Scene Photography by

Professor Bob Warnock

and Jerry Dambrogio

Gunshot residue (GSR), or more technically, gunshot primer residue, is expelled as tiny particles from the barrel of a firearm when it is fired. Among other materials, gunshot residue contains the heavy metals barium, lead and antimony. Modern forensic methods require the presence of these metals to identify trace evidence as gunshot residue.

Through the 1990s the presence of two or more of these heavy elements was sufficient to conclude the chemicals were the result of a gunshot. New, more rigorous standards for gunshot residue testing are now being required by many courts. The trend is toward a standard that requires the presence of at least one Pb-Ba-Sb particle (lead-barium-antimony) exhibiting characteristic GSR morphology and supported by a sufficient number of atomically identified GSR supporting particles in the remaining particle population.

Investigators may test a suspect's hands, arms and face for particles of gunshot residue as evidence of having recently handled or fired a gun. Current testing methods are inconclusive as a suspect's clothing or body can easily become contaminated after the firing from sources such as being handled by police officers or being transported in contaminated police vehicles

Suspect

Scene Weapon

Victim

Suspect

Scene Weapon

Victim

- Materials which are emitted from a firearm when it is discharged.

- Materials which are emitted from a firearm when it is discharged.

Distance determination “Was the victim

shot at close range?”

Distance determination “Was the victim

shot at close range?”

Identification of bullet holes “Is the damage

due to the passage of a bullet?”

Microscopic examination Smokeless powder Fiber damage

Association with a firearm discharge “Who fired the gun?”

There has been a critical need for a reliable and accurate way to associate a suspect with a firearm discharge

1933 Teodoro Gonzalez Criminal Identification Laboratory- Mexico

City Police Headquarters Gonzalez test Paraffin test Paraffin glove test Diphenylamine test Dermal nitrate test

Nitrates

SAMPLE