I haven't dealt with this subject in regards to shooting, BUT, I have in traffic accidents.
I did a bit of Fatality Traffic Investigation in my LE Career. I do know for a fact that if you're involved as a driver and some one is killed they will get a warrant and do a drug/alcohol test.
Weather or not you are responsible for the accident, if you have drugs in your system (not necessarily high but lets say pot in your system from several days ago) you can bet your whatever, that its gonna hurt you, maybe not in a criminal case but it will in a civil case.
I don't care (within reason) what another person does, but it can come back to bite you.
I personally don't worry about it, I made it 65 years without it, I figure I can make a few more.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071