Oh, the excuses one hears as well... "I ate a lot of poppy seed rolls for dinner...", "I was at a party in the enclosed cabin of a small sailboat, it was raining, and though some were passing a big joint around, I didn't smoke any...", and of course there's the tried "I didn't inhale."

Maybe a standup or a lean-to is about how one gives the sample? Or they test when the stand-up can't anymore and begins to lean-to (probable cause)?

On a slightly more serious vein, maybe the three-week notification was actually for a periodic, and not a random?