are you there?
mass spectrometery is nearly foolproof.
you will never get someone to admit, even in a court of law, that they used a drug if they are just not going to admit it.
false positives can occur with even the most accurate test....
but the likelihood of this test being falsely positive is so remote as to be ridiculous.
i would never take this bet.
but if you look long enough you will find something to support your side of the arguement...
my money is on true positive.