Explosives experts at the US Department of Energy’s Sandia National Laboratories, working with a Colorado company, have come up with a technique that will help police officers at a crime scene quickly narrow the list of suspects in a shooting to those who have recently fired a gun.
‘Police don’t have anything today that can tell them instantly whether someone has fired a gun or not,’ said Greg MacAleese, CEO of Law Enforcement Technologies, Inc. (LET) of Colorado Springs. ‘The speed in being able to focus on a more limited array of suspects is really critical to law enforcement’s ability to solve a crime. The faster we are able to ID them, the more likely we are to convict them.’
Whenever a gun is fired, the shooter gets sprayed with an invisible blast of chemical residues that are by-products of the incomplete combustion of gunpowder, primer, and lubricants. The Sandia-LET gunshot residue detection technique reportedly identifies very small amounts of these chemical clues on a person’s hands, arms, or clothing.
‘With this technique a police officer could swab somebody right at the crime scene and have a reading in seconds,’ said Sandia principal investigator Pam Walker.
In laboratory and live-fire trials at Sandia the technique was effective in determining if someone had recently fired a gun, regardless of whether the shooter had washed his or her hands after the shooting. Various gun and ammunition types were used.
Each LET gun residue detection kit includes a round fibreglass swab that can be rubbed on the hands, arms, or clothing of someone suspected of firing a gun. The police officer places the dry swab into a small plastic cube, pushes a plunger button on the lid that breaks a vial inside the cube to release a clear liquid, which soaks the swab.
If gun residue is present, spots where trace amounts of organic residues are present turn blue against the white swab, typically in 40 to 60 seconds.
Roughly the size of a cassette tape, each LET kit should cost less than $20, according to MacAleese. Positive results from the kits could be used to influence a suspect to confess or to implicate other suspects. In addition, the same swab used at the scene can be sent to a forensics lab for additional chemical analyses, the results of which could be used as evidence in court, he said.
Police officers investigate some 13,000 firearm homicides in the United States every year, and approximately 40,000 patients with gunshot wounds resulting from assault are treated in US emergency rooms annually, according to 1997 statistics from the US Department of Justice.
Detectives know that the first 72 hours are the most critical time for the successful investigation of a crime, said MacAleese. Every minute a shooter stays out of police custody is a minute he or she can spend destroying evidence, establishing alibis, or leaving town, he said.