Blood alcohol concentration (BAC) is a hot topic where drunk driving is concerned. It takes a certain level to get you arrested (usually), and another level to raise the charges to more serious ones. Patrol officers give preliminary breath tests, police give more accurate ones at the station, and there are blood and urine tests too. The numbers matter to everyone: judges, prosecutors, and defence.
What makes it tough is that the numbers can be deceptive. You might have two or three drinks and be just under the legal limit. But a half hour later, your BAC has actually gone up, and you’re legally intoxicated.
How can it happen? In fact, it’s very normal for one’s blood alcohol level to creep up after drinking. The body can take a while to absorb alcohol, especially on a full stomach. It’s very possible to be drunker an hour after finishing that last drink. This means you could get into the car with a BAC of .07, but by the time a police cruiser pulls you over, you will blow an .09 into the breathalyzer.
Things to consider: if you get behind the wheel at .07, you’re already in trouble in some provinces. Ontario, for instance, has a “warn range” of between .05 and .07 BAC. If you register in that range, you will face provincial administrative penalties. These will include fines and suspension, and could include mandatory alcohol education and an ignition interlock.
Think about this as well: you could be arrested with a BAC under the limit under a number of circumstances – impairment doesn’t necessarily involve being over .08 – but by the time you’re tested at the station you are in the intoxicated range. While you sat handcuffed in the station, your blood alcohol level actually continued to climb.
You might claim that you were not drunk at the time you were driving – your BAC crept up after your arrest. This claim, known as the bolus defence, is hard to prove, as you need witnesses or evidence to prove how much you had to drink and when.
BAC is a slippery thing. Everyone’s body absorbs alcohol at a different rate, and displays impairment at a different rate. The smart strategy is never to get anywhere near the .05 warn range when you are driving. Designate a driver, take a taxi, or wait long enough for the alcohol to leave your system. Do that and there’s no need to dread the breathalyzer test.