The Baltimore Banner reports on a recent ruling from the Supreme Court of the state of Maryland, which states that it is no longer admissible in court for so-called expert witnesses to testify that a specific bullet was fired from a specific gun. From the article:
Firearm identification asserts guns leave unique patterns and marks on bullets, the opinion said, and that experts can use them to link casings from a crime scene to a specific gun.
Chief Judge Matthew Fader, who wrote the ruling, noted that the majority doesn't question that firearms identification is generally reliable. He wrote that it can be helpful to a jury in identifying whether patterns and markings on "unknown" bullets or cartridges "are consistent or inconsistent with those on bullets or cartridges known to have been fired from a particular firearm."
Based on the record here, and particularly the lack of evidence that study results are reflective of actual casework, firearms identification has not been shown to reach reliable results linking a particular unknown bullet to a particular known firearm," Fader wrote.
Several justices dissented, arguing that such firearm identification has been the "backbone of countless prosecutions," an historically reliable legal device for sending people to jail.
And there's the rub: these kind of ballistic testimonies have indeed been used in many prosecutions, and have helped to send many people to jail. But that's not necessarily a good thing. While this particular ruling might sound like an olive branch to violent gun enthusiasts, the truth is that a lot of what we call "forensic evidence" is essentially a Zodiac reading for the criminal justice set. As Scientific American reported in 2022:
Firearms examiners suffer from what might be called "Sherlock Holmes Syndrome." They claim they can "match" a cartridge case or bullet to a specific gun, and thus solve a case. Science is not on their side, however. Few studies of firearms exist and those that do indicate that examiners cannot reliably determine whether bullets or cartridges were fired by a particular gun. Firearms identification, like all purportedly scientific proof, must adhere to consistent and evidence-based standards. Fundamental justice requires no less. Absent such standards, the likelihood of convicting the innocent—and thus letting the guilty go free—is too great. It is perhaps this realization that has led courts to slowly start taking notice and restrict firearms testimony.
2009 National Research Council (NRC) report criticized the firearms identification field as lacking "a precisely defined process." Guidelines from the Association of Firearm and Tool Mark Examiners (AFTE) allow examiners to declare a match between a bullet or cartridge case and a particular firearm "when the unique surface contours of two toolmarks are in 'sufficient agreement.'" According to the guidelines, sufficient agreement is the condition in which the comparison "exceeds the best agreement demonstrated between tool marks known to have been produced by different tools and is consistent with the agreement demonstrated by tool marks known to have been produced by the same tool." In other words, the criterion for a life-shaping decision is based not on quantitative standards but on the examiner's subjective experience.
(That same Scientific American article presents what I think is an interesting metaphor, comparing Firearm Examiners to hospital nurses: "If you need a COVID vaccine, the nurse has the right form of expertise. By contrast, if you want to know whether the vaccine is effective, you don't ask the nurse; you ask research scientists who understand how it was created and tested.")
PBS' Frontline reported on the same issue 10 years earlier, while also offering similar criticisms of both fingerprinting and bite mark evidence:
One fundamental problem with ﬁrearms analysis is the lack of a precisely deﬁned process, the National Academies of Sciences found. An examiner may offer an opinion that a speciﬁc tool or ﬁrearm was the source of a speciﬁc mark when "sufﬁcient agreement" exists in the pattern of two sets of marks, but there is no precise definition for that statement. The NAS also found there have been no scientific studies to answer questions regarding variability, reliability, repeatability, or the number of correlations needed to achieve a given degree of conﬁdence.
This 2015 article from ThinkProgress also offers some specific anecdotes of real-life incidents where forensic evidence, including fingerprinting and ballistic testimonies, led to wrongful convictions. As much as this sounds like a state Supreme Court further loosening gun laws in America, it may ultimately prove to be a progressive move for criminal justice reform.
Supreme Court of Maryland rules firearm experts can no longer testify a bullet came from a specific gun [Cadence Quaranta / Baltimore Banner]
The Field of Firearms Forensics Is Flawed [David L. Faigman, Nicholas Scurich, Thomas D. Albright / Scientific American]