Call me naive but I'm open to the 'poisoned' line of defence.
Just got back from an early morning ride and while I was out I was thinking about something someone on TheClinic said (yes, I know.....
) . Shack are on the point of imploding, contracts haven't been honored and wages haven't been paid. Frank and Andy are star riders and must be on massive salaries. The boss of Shack goes to the team doctor and asks if they can slip something to Frank in his food or drink, nothing dangerous, just a masking agent that's easily detectable, then when he's tested positive we can wash our hands of him and save a couple of million.
Might not be that far fetched?