You are forgetting that criminals will alter their behavior in response to laws. Possible counter measures include:
- grinding the head of the firing pin to remove the stamp
- picking up your brass or use a revolver
- carrying a hand full of brass from a local gun range and dumping at the scene.
- using reloaded brass
- swamping out the firing pin
Ugh. I guess that is why there are so many unsolved murders. It is impossible to beat the killer.
Going to the range and policing up YOUR brass to then seed the crime scene with.