  Since the National Academy of Sciences released their report outlining paths
for improving reliability, standards, and policies in the forensic sciences NAS
(2009), there has been heightened interest in evaluating and improving the
scientific validity within forensic science disciplines. Guyll et al. (2023)
seek to evaluate the validity of forensic cartridge-case comparisons. However,
they make a serious statistical error that leads to highly inflated claims
about the probability that a cartridge case from a crime scene was fired from a
reference gun, typically a gun found in the possession of a defendant. It is
urgent to address this error since these claims, which are generally biased
against defendants, are being presented by the prosecution in an ongoing
homicide case where the defendant faces the possibility of a lengthy prison
sentence (DC Superior Court, 2023).
