OK, so here are some questions I’d be asking if I were his lawyer:-
The amount detected was 400times lower than the required lowest detectable level. If most labs / assays can only detect a higher level how has this test been validated?
What is the half life of the substance? If it’s such a low urine/blood concentration than its likely to have been either a tiny amount he ingested (which would support contamination) or it’s been in his system for ages – at which point could another test have picked it up previously.
The problem is as assays get more accurate – the results become harder to interpret. For instance who would want to be fired from work if they did random drug testing and found cocaine in your system from a dollar bill you touched two weeks ago? This is pretty much his argument (not about cocaine mind….).
But, as I said, I’m jet lagged and it’s been a long time since I worked as a pharmacokineticist.