How Reliable is Gunshot Residue Testing in Maryland Courts?

 Posted on September 19, 2025 in Weapons Crimes

Although gunshot residue (GSR) evidence is often used in court by prosecutors to convince a jury of an individual’s guilt, the reliability of GSR evidence has been repeatedly questioned. The reliability of GSR is under near-constant siege and is used to indicate exposure to a fired gun. Although particle characteristics of lead, barium, and antimony are considered almost irrefutable evidence by jurors, the presence of these elements can conceivably come from other sources.

GSR is easily transferred, can be removed by washing, is degraded by normal activities, and does not rule out firing a weapon. Because of this, GSR evidence should be viewed as corroborating evidence rather than standalone "proof." If you have been charged with a criminal offense that involves a firearm, consulting with a highly experienced Harford County, MD criminal defense lawyer is the best step you can take to protect your future.

Potential Issues Associated with GSR Evidence

Some of the limitations associated with GSR evidence include:

• The metals found in GSR (lead, barium, and antimony) can trigger false positives because these same metals are also present in industrial environments, brake dust, and fireworks.
• GSR particles can transfer from a firearm, shooter, or crime scene to others who were not near the actual discharge. This is known as secondary transfer.
• GSR particles are fragile and can disappear rapidly from handwashing, wiping surfaces, or regular physical activity.
• The length of time that GSR will remain on an individual or his or her clothing can depend significantly on weather, temperature, and the clothing materials.
• A GSR analysis only indicates proximity to a discharged firearm, not absolute confirmation that a specific person fired the weapon.
• Scientific methods used to analyze organic compounds from gunpowder lack universal standards.
• Since GSR is rarely conclusive by itself, the experts must provide detailed testimony regarding the analysis, sample collection, and the statistical likelihood of the findings, which is often complex for jurors to interpret.
• Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) both require expensive equipment and many hours to analyze a single sample.
• The amount of GSR deposited on an individual from a gun firing will vary widely, depending on the environment, the ammunition, and the gun.
• Some newer ammunition types lack the heavy metals that GSR tests look for.

What Are Daubert/Frye-Reed Admissibility Issues?

Daubert and Frye-Reed admissibility issues (Federal Rules of Evidence 702) refer to the legal standards used by judges to determine whether scientific evidence or expert witness testimony can be presented in court. Federal courts and most state courts follow the Daubert standard, while a handful of states continue to use the older Frye standard.

The Daubert standard gives judges discretion to determine whether an expert’s testimony is both relevant and reliable to the facts of the case. Daubert tends to be a more flexible standard, allowing for the admission of newer, innovative scientific techniques.

The Frye standard holds that scientific evidence is admissible only if the technique or theory on which it is based is generally accepted by the relevant scientific community. During a special hearing, the challenging party will argue that the opposing expert’s testimony is irrelevant or unreliable and should be excluded.   

Contact a Northern Baltimore County, MD Criminal Defense Lawyer

Although gunshot residue certainly sounds persuasive, the methodology and results are far from foolproof. GSR is fragile, easily contaminated, and open to interpretation. The reliability of GSR should always be questioned, and courts should ensure that jurors are aware of the technology's limitations.

If you or a loved one is facing gun crime charges in Maryland and the prosecutors are relying on GSR, you need to speak to a knowledgeable Harford County, MD gun crimes attorney from Baltimore Legal Services. Our attorneys know how to challenge unreliable forensic science, cross-examine state experts, and fight for your rights. We are available 24/7 and have helped more than 10,000 clients achieve the best possible outcome. Call 858-523-8423 to schedule your free consultation.