
I'm not a criminal but from what I gather
A good criminal must be careful to never leave loose ends when dirt is being done.
Anybody that sees your face when you're doing dirt – especially dirt that will get you 25+ – has got to go because 9.5/10 they'll either call the cops on you or, in case you get them shook on the spot - they'll stay quiet for a few days until a friend/family-member/cops/victim-family convinces them to step forward.
Letting the person that's seen you commit a crime go is usually the same as dropping a clue in front of a police station because there will be an APB on your ass.