Labs-tested gun residue detection technique will help cops ID shooters right at the crime scene
When people gather at the scene of a violent crime, police officers investigating the crime typically hear a lot of "he said, she said." Either that or nobody saw nuthin’.
Now Sandia explosives engineers, working with a company that specializes in police gadgetry, have come up with a technique that will help officers at the crime scene quickly narrow the list of suspects in a shooting to those who have recently fired a gun.
The field test kit for gunshot residue detection will be available to some law enforcement agencies this month, says Greg MacAleese, CEO of Law Enforcement Technologies, Inc. (LET), the
Colorado Springs company that licensed from Sandia the chemical detection technique that makes the kits possible.
"Police don’t have anything today that can tell them instantly whether someone has fired a gun or not," says MacAleese. "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." (See "At fresh crime scenes, minutes matter" on page 4.)
In trials at Sandia the technique was effective in determining whether someone had recently fired a gun, regardless of whether the shooter had washed his or her hands after the shooting.
LET plans to test the first 2,000 field kits with police departments in New York state and the Los Angeles, San Diego, and Phoenix metro areas beginning this month.
Whenever a gun is fired, the shooter gets sprayed with an invisible blast of chemical residues that are byproducts of the incomplete combustion of gunpowder and lubricants.
Each LET gun residue detection kit includes a round fiberglass swab that can be rubbed on the hands, arms, or clothing of someone suspected of firing a gun. When the swab is soaked in a proprietary clear liquid chemical, spots where trace amounts of organic residues are present turn blue against the white swab.
"We routinely do trace detection of explosives in the lab," says principal investigator Pam Walker (2552), "so we thought why not take this technique and make it a product that can help keep our streets safer."
MacAleese, a former violent-crime detective who is working with Sandia on several law enforcement technology projects, funded the Sandia test program.
To examine the technique, Pam and Phil Rodacy (2552) lab tested two colorimetric approaches to detecting gun residue on a person, one seeking to detect the organic constituents of gun residues, the other to detect inorganic residues.
Live-fire field tests at Sandia’s Terminal Ballistics Facility in Area 3 and at Caliber’s Indoor Shooting Range in Albuquerque confirmed that the swabs indicated the presence of organic gun residues on a person’s hands 75 to 90 percent of the time, regardless of how many times the shooter pulled the trigger. Various gun and ammunition types were used.
Cheap, simple, portable
After swabbing the suspect, the officer places the dry swab into a small plastic cube much like a toy bug-magnifying kit. The officer pushes a plunger button, which breaks a vial inside the cube and releases the clear liquid, which soaks the swab. If gun residue is present, the blue spots appear, typically in 40 to 60 seconds.
"The idea is that a rookie police officer without any training could swab somebody right at the crime scene and have a reading in seconds," says Pam.
Roughly the size of a cassette tape, each LET kit should cost less than $20, according to MacAleese, who says the kits will be marketed under the name "Instant Shooter ID Kit."
"We’d like to see these kits not only in every forensics lab and violent crime unit but also in every squad car in the country," he says.
At this point, says MacAleese, the kit results are not admissible as evidence in a court of law, but pinning the crime on individuals more quickly would help officers convince suspects to confess or to "squeal" on 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 in court, he says.
A new capability
"We were surprised to learn that police officers didn’t have a way of detecting gun residue at the crime scene," says Phil.
Most metro crime labs typically don’t have the expensive microscope equipment needed to detect gun residue. Police departments end up shipping samples out to busy state police crime labs or contract laboratories and waiting weeks for results, and only in the most high profile cases, he says.
"This technique could make identification and verification of suspects using gun residue detection a common practice at shootings," adds Pam.
Other Sandians involved in the project include Terminal Ballistics Facility staffers Dave Paul, Mike Bernard, and Roy Dickey (all 2554), who assisted with the live-fire tests; Susan
Bender (2552), who assisted with the project management and patent application; and Kevin McMahon of Licensing & Intellectual Property Management Dept. 1321, who prepared the licensing agreements.