First use of forensic tests on firearms?
Just came across a page I'd copied long ago, a Tenn. Supreme Court case from 1842 December Term. (Don't have number of volume, but pp are 290-91, and case is Kirby v. State). Basically, a Ms. Todd was shot at night, through her window. A "very much mashed" rifle ball was found in the room.
"William Daniel proved that the made the bullet moulds for Gideon Anderson's gun, and had in his possession a bullet that was run in those moulds, and by a mark which the moulds make near the neck of the bullet, he knew that the round bullet in his possession, and the mashed bullet found in the house of the deceased, were run in the same mould because they were just alike as to said mark." He also verified the weights were identical. It was proven that Anderson had just sold his rifle to defendant, together with a stock of cast balls.
Shoe marks on ground also matched defendant's shoes, and horse tracks that matched (defendant's mare had a peculiarly shaped hind foot).
The court held that these data, together with defendant's evasive and changing story as to where he was, established guilt.