I suspect someone at work of taking cocaine but if I swabbed the toilet next to his office and it came up positive could it just be from something like a banknote?
Would a positive test indicate that drugs had definitely been taken in there or perhaps by this person at a party a week earlier and it was still on their hands?
If it was positive how long would it be in their system for a real drugs test to show?
I am trying to say that are all say office bathrooms full of traces of cocaine from banknotes etc or would it be a "smoking gun" of proof.
Yeah don't do this.
There's zero way to prove that something on a toilet is related to this individual and the only person that is going to get in trouble or look insane is you.