[AppyPappy]

Your BAC drops over time.

[Domangart]

Yes, if that was all they tested for then thats all the lab work there is. This is why observation is a big deal.

[Smokin' Joe]

Yep. Approximately one drink's worth every hour. Of course, the amount of that 'drink's worth' depends on your body weight. (The higher the body weight, the less the change.)

It takes about 45 minutes to reach a postabsorbtive state, where BAC maxes out and the alcohol is evenly distributed in the body. Many states have provisions for DUI even though the BAC is lower than legal thresholds.

A lot depends on the driver's attitude toward the police,