Worse than useless, worse than expensive.... down right miss leading.
A criminal plans to kill someone.
Goes to a local range and finds fired brass from the same caliber. Uses micro-scope to find one case that has a stamp on it. Goes ahead and commits the crime. Drops the wiped down case at the crime scene.
Cops spend days / weeks harassing an innocent gun owner.
Very good point. Hopefully a smart detective will take into consideration the fact that the brass has been fired multiple times before going for a conviction, but you’re right, they will be at least hassled.