Gun Shot Residue Evidence – Not Always A Smoking Gun!

To a layperson – and member of a jury – gun shot residue evidence sounds extremely incriminating. After all, it supposedly proves that a suspect has recently fired a gun or been very close to a fired gun. But, in actuality, gun shot residue (“GSR”) evidence is not always so clear-cut.

Gunshot residue testing

Gun shot residue is tested by lifting samples off a defendant’s hands or clothing and then testing to see if the lifts contain a fused particle of barium, antimony, and lead, which are known to be present in GSR. However, even if a GSR test comes back positive, there are numerous issues that can impact the strength and reliability of such evidence.

First, in every GSR test report – whether the test comes back positive or negative for GSR – there is always a disclaimer. A positive GSR test result does not necessarily mean that a defendant has fired a gun. Even if the fused particles of barium, antimony, and lead are found, they could have come from other materials, such as brake pads or fireworks, or they could be a result of a contaminated sample. Similarly, a negative GSR test result does not necessarily mean that a defendant has not fired a gun. The GSR particles could have been washed away or the Defendant could have been wearing gloves. So, in actuality, what does the GSR test really prove?

Second, it is important to consider how the GSR sample was collected. Many times, police officers do not gather the GSR samples in a proper way to prevent the possibility of contamination. The FBI and most police departments recommend that GSR samples be taken from a suspect immediately at the scene and hopefully before being handcuffed or transported in a police cruiser. Studies in major metropolitan areas around the country have determined that there are an alarmingly high number of GSR particles on handcuffs, the back seats of police cars, holding cells, interrogation tables and chairs, as well as on police officers themselves. See Baltimore Sun Times Special Report , Stephanie Hanes, Evidence Under Suspicion , Jan. 23, 2005 (noting Baltimore testing of police departments revealed GSR in interview rooms, on tables, on chairs, and in the air and also that an internal Los Angeles Police Department test found that police cruisers were contaminated by GSR and that the particles transferred onto people who hadn’t fired anything); Berk et al, Gunshot Residue in Chicago Police Vehicles and Facilities: An Empirical Study (2007), 52 J. Forensic Sci. 838); Thompson & Nethercott, “Forensics”, The Champion(June 2005), at 50; FBI Symposium (Report of Dr. Jon Nordby). These studies determined that defendants may easily be contaminated with GSR residue when held in police custody prior to testing. See id.

This high potential for contamination has prompted a more intense focus on GSR sample collection procedures. For example, in the 2005 FBI Symposium, participants unanimously agreed “that GSR sampling should be done at the scene, where permissible, and as expeditiously as possible.” 2005 FBI Symposium at 4. Further, if samples cannot be obtained at the scene, then a suspect’s hands should be placed in plastic protective bags before being placed in a police vehicle. See id. If a defendant’s hands are not sampled at the scene and are not bagged prior to transport, the likelihood of contamination greatly increases. As the Director of the Baltimore, Maryland crime lab stated, “If they don’t bag them, we don’t test them.” See Baltimore Sun Times Special Report, Stephanie Hanes, Evidence Under Suspicion, Jan. 23, 2005.

Further, numerous other courts have held that contamination of samples make GSR evidence unreliable. For example, the Washington Supreme Court reversed a murder conviction and remanded for a new trial based in part on unreliable GSR evidence. In re Stenson, 174 Wash.2d 474, 480-483, 276 P.3d 286, 290 – 291 (Wash. 2012). In Stenson, the Washington Supreme Court noted the GSR evidence on the suspect’s jeans could have been contaminated because pictures of the jeans show that they were handled by a ungloved police officer and traveled to numerous laboratories, including the FBI Laboratory in the Hoover Building in Washington D.C., which is a facility that contains two shooting ranges and is known to be contaminated with GSR, before any GSR testing was done. Id.

So, the bottom line: any criminal case that involves GSR evidence should be carefully analyzed. A criminal defense attorney needs to be aware of the potential for a false positive GSR test result, as well as the risk of contamination from an improperly collected sample. And, in all cases, a jury should be informed of the very limited probative value of GSR testing results.

If you are facing gun and weapon-related charges, let Scott & Nolder Law Firm represent your interests in court.