Determining a Driver’s Blood Alcohol Level

Blood alcohol testing is an attempt by law enforcement to determine how much alcohol is in a driver’s bloodstream. If a blood alcohol test result is 0.08% or higher, a driver is presumed to have violated the law (Vehicle Code 23152(b)). Keep in mind that the defense can present evidence, either through cross examination or affirmatively, that the test result is unreliable. It is important to remember that the blood alcohol test is supposed to determine the driver’s blood alcohol concentration at the time of driving the car, and not after the fact. There can be a significant difference between a driver’s blood alcohol concentration at the time of driving and the time the test is taken, which sometimes occurs an hour or more later.

The two most common tests that a law enforcement officer uses to determine a person’s blood alcohol concentration is a breath test, where the driver blows into a device; and the blood test, where the driver’s blood is drawn for analysis. Various factors such as gender, the amount of alcohol consumed, the person’s weight, the type of alcohol that was consumed, the time of consumption, and any food consumption, can directly impact the reliability of the results of these tests.

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