Doesnt work that way. No system allows for others to claim responsibility. If it went in your body, it doesnt matter how it got there, all that matters is that its there. It seems unfair, but unfortuantly, to stay neutral and not allow stuff like you are describing, it has to be concrete.
It does remind me of this guy I worked with when I was in the Navy. His wife had made pot brownies for her an some friends. He knew she partied once in awhile. He never, ever, ever touched the stuff cause he didnt want to lose his job. He has 2 kids, so losing his job was out of the question. Anyway, one day after she had made some for her friends, he ate one not knowing she had made them. He knew about 30 minutes later, called his wife, she confirmed it. She was completely apologetic. They decided tell someone about it and try and claim innocence and guilt right away before being caught. Didnt matter. Their chief was actually pretty cool and told them to just flush (his system) as much as possible and hope his name didnt pop randomly on a drug test. It did. He was other then honorably discharged. This guy was a saint and everyone knew it was accident, but there was nothing they could do.
Time of possession is the most meaningless statistic in football. -RolandDeschain