The legal limit for blood alcohol content (BAC) in Oregon is .08 percent by weight of alcohol in the blood. Thus, a BAC of .08 or higher, at the time of driving, would make you guilty of a DUII in Oregon.
A .08 is a .08 and That’s it
This is true whether you felt “impaired” or not… a .08 is a .08 and that’s it. So, .08 or higher at the time of driving is guilt. In Oregon, breath tests by the intoxilizer machine are conducted at the police station. Therefore, inherently, there is a delay between the time of arrest and the time you provide a breath test sample.
This delay can be even greater when a person is arrested after driving (i.e. someone called the police on a suspected DUI driver and then the police arrest the person at their house). Alcohol does not stay consistent in your system.
Alcohol in Your System
Your body first must absorb the alcohol and then, once it’s absorbed, the alcohol must dissipate in your system. Therefore, while your breath test sample may be a .07 or lower when you provide a sample at the station, your BAC likely was different at the time you were driving (30 minutes to even an hour or more later). In this case, experts will attempt to extrapolate back to determine what your BAC would have been at the time you were driving.
Alcohol follows a bell curve in your system. However, this is not a perfect science and not every person’s bell curve is the same. Thus, backward extrapolation likely cannot give you an exact amount, as every person’s metabolism, weight, water in the body, etc. are different. The police and prosecutor are going to try to suggest your BAC was higher though and a jury, or judge, should assume you were higher at the time of driving than you were when a breath test sample was provided at the station.
Of course, the prosecutor also could try to establish you were “impaired to a perceptible degree” regardless of the result of a breath test. Some people will be impaired by alcohol prior to their BAC reaching .08.