Does science support a firearms and tool mark expert from saying anything more than that “the firearm may have fired the recovered casing … ? Not, “it came from this gun and no other,” or “casings from the crime scene and from test fires of the suspect’s gun match,” but a much more calibrated and restricted conclusion, evidence that is probative but not determinative.

According to a September 2019 ruling, the “may” finding is the limit. “The government’s expert may testify that based on his examination, the recovered firearm cannot be excluded as the source of the cartridge casing found on the scene of the alleged shooting,“ see United States v. Tibbs, 2019 D.C. Super. LEXIS 9, *80.