Md. Supreme Court imposes limits on ballistics evidence used to link guns to crimes
Four of seven justices found the scientific methodology is not reliable enough to allow examiners to testify that a particular gun fired a particular bullet
By Alex Mann
The Baltimore Sun
BALTIMORE, Md. — In Maryland, firearms experts will no longer be allowed to testify that a specific gun fired a specific bullet, the state’s highest court ruled in an opinion published Tuesday.
Authored by Chief Justice Matthew J. Fader of the Supreme Court of Maryland, the opinion imposes limits in the courtroom on the practice known as firearm “tool mark” analysis. The forensic technique postulates that machines used to make guns leave tiny imperfections on their components, and that those components imprint unique marks on ammunition — composed of softer metal — when fired.
Until now, it was commonplace for firearms examiners — usually employed in police crime labs — to testify that a gun recovered by law enforcement fired bullets or casings found at a crime scene, if they believed that to be true based on their observations under a microscope.
But four of seven justices on the state Supreme Court found that the scientific methodology is not reliable enough to allow examiners to testify that a particular gun fired a particular bullet. Examiners can, however, testify “that patterns and markings on bullets are consistent or inconsistent with those on bullets fired from a particular known firearm,” the opinion said.
The ruling responds to the appeal of a murder case in Prince George’s County, but all decisions by the state’s highest court are binding on lower courts.
One of the attorneys behind the appeal, Stanley Reed, described the legal team as “very gratified.”
The Maryland Office of the Attorney General, which represented the state in the appeal, did not immediately respond to a request for comment Tuesday evening.
With the opinion, Maryland becomes one of the first jurisdictions in the country where an appellate court has recognized shortcomings in the forensic practice and imposed limits on its use in court, according to experts.
Maneka Sinha, an associate professor at the University of Maryland Francis King Carey School of Law who studies forensic sciences, said the justices “came to the conclusion that scientists, academics and others seriously studying the discipline already have: that conclusions claiming they can say a specific gun fired a specific item of ammunition are simply unreliable.”
“These kinds of unreliable conclusions have been central to prosecutors securing countless convictions — convictions we should all be questioning now,” added Sinha, who successfully argued for one of the first limits placed on firearm analysis testimony in a case from the Superior Court of the District of Columbia cited in the Maryland appeal.
Jeffrey Gilleran, chief of the forensics division at the Maryland Office of the Public Defender, echoed Sinha’s comments.
“For too long has the criminal legal system allowed unvalidated and unreliable methods to be admitted at trial,” Gilleran said in an email. “This opinion is a step in the right direction and we look forward to this type of in-depth analysis for other forensic disciplines, even those that have long been considered settled.”
When there is a shooting, police typically cordon off the area with crime scene tape. Crime lab technicians respond to mark evidence, photograph it and collect it. Then, they take it back to the crime lab for further testing. Key among that evidence is usually fired cartridge casings.
A casing encapsulates a bullet. After a trigger is pulled, a firing pin rams the back of the casing, which ignites an explosive substance inside. That propels the bullet down a barrel, which features twisted metal known as “rifling” inside, to spin the projectile for accuracy. A semiautomatic handgun ejects a casing after each shot.
If a gun is recovered during an investigation, firearms examiners test-fire the gun. Then they use comparison microscopes, which allow them to look at two pieces of evidence simultaneously, to compare bullets or casings picked up at the crime scene with those from the test fires. They then decide whether they believe there are enough markings on the spent projectiles to declare a match.
The Association of Firearm and Tool Mark Examiners says examiners can declare a match when an examiner sees “sufficient agreement” between two projectiles. The organization, which establishes standards for the field, says agreement between two rounds is significant when a set of markings is of “a quantity and quality that the likelihood another tool could have made the mark is so remote as to be considered a practical impossibility.”
There are five conclusions an examiner can reach: elimination of a bullet as having been fired from a specific gun, identification of a projectile being fired by that gun and “inconclusive.” There are three types of inconclusive findings an examiner can cite: one that leans toward excluding a match, one that leans toward a match and one that represents greater uncertainty.
Proponents of the practice say that firearms examiners rarely declare a match incorrectly.
But how often examiners’ findings are wrong is a subject of great dispute. Lawyers on either side of the appeal pointed to studies with error rates ranging from zero to 50%.
That discrepancy likely has to do with how “inconclusive” findings are counted. Critics say that most firearm analysis studies count inconclusive as correct, artificially inflating the error rate.
One of the three dissenting justices, Steven B. Gould, wrote that the court shouldn’t worry about inconclusive findings.
“Our concern is this: when the examiner does declare an identification or elimination, we want to know how reliable that determination is,” Gould said in his dissenting opinion. “The record shows that conclusive determinations of either kind (identification or elimination) are highly reliable.”
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