Imagine that while driving through York, you are stopped by a law enforcement officer. You did have a drink a few hours past, yet felt as though you waited a sufficient amount of time for it to not affect your judgment or your driving abilities. When asked to take a breathalyzer test, however, you register a blood-alcohol content reading of 0.08 percent, which you know is enough to be arrested for DUI. Yet an hour later, a blood test is administered which shows your BAC to be 0.02. You see this as proof that the earlier test was wrong. Your arresting officer, however, says that your body has just metabolized the alcohol in that time. Is that possible?
To answer this question, you need to understand how alcohol interacts with your body's system. According to information shared by Brown University, when you consume alcohol, 20 percent of its content is absorbed by your stomach, with the rest being absorbed by the small intestine. It is them metabolized by the liver, which can process roughly one ounce of alcohol per hour. The rest accumulates in your body tissues as well as your bloodstream waiting to be metabolized. To reach the 0.08 threshold, it may take an average 175-lb person about three drinks.
In terms of BAC concentration, the liver metabolizes roughly .015 percent per hour. Thus, in the example shared earlier, if the initial breathalyzer reading taken was indeed accurate, your BAC should still be around 0.065 after one hour. The fact that a blood test (recognized to be the most accurate way to measure BAC) shows it to be 0.02 could serve as a strong indicator of an incorrect initial reading. Indeed, some estimates of breathalyzer accuracy assign them a margin of error rate as high as 50 percent.