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.

In the courts, firearms examiners present themselves as experts. Indeed, they do possess the expertise of a practitioner in the application of forensic techniques, much as a physician is a practitioner of medical tools such as drugs or vaccines. But there is a key distinction between this form of expertise and that of a researcher, who is professionally trained in experimental design, statistics and the scientific method; who manipulates inputs and measures outputs to confirm that the techniques are valid. Both forms of expertise have value, but for different purposes. 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.