Is There a Time Limit For The Police To Draw My Blood As Evidence?

 Posted on May 07, 2020 in DUI

In Arizona, officers must draw your blood within two hours of you being pulled over for suspicion of DUI if they wish to use the blood results as evidence against you. That’s because the law says you cannot have a prohibited alcohol concentration within two hours of driving or being in actual physical control of a car. The police are aware of this short window and will try to draw your blood as quickly as they can. However, in some cases, a driver’s blood is not taken until 2 hours after the stop. In fact, it is not unusual for testing to occur outside the 2-hour window.

Even if the police miss the two-hour window on drawing your blood, they can still try to use the results as evidence against you by relying on something called retrograde extrapolation. This scientific process determines if you had a BAC of .08 or higher within two hours of driving. Usually, the State will have a chemist testify using the blood result and guess backwards as to what your BAC would have been within two hours of driving.

However, retrograde extrapolation has been criticized by many experts in the field. Some argue that this method requires a chemist to make several assumptions. For example, chemists often assume that the alcohol was completely absorbed at the time of testing, or that the alcohol curve was charted correctly, or that the alcohol in your system was eliminated at an average rate. These are major assumptions that may be wrong and affect the results of the chemist’s BAC estimation.

The truth about retrograde extrapolation is that many factors may lead to an incorrect estimation of BAC in a driver at a certain time. The rate of alcohol consumption can be altered by your body temperature, the type of alcohol drink you consumed, the amount and type of food you age, and your weight and gender.

An experienced attorney will be able to challenge the State’s retrograde extrapolation and demonstrate it for the “dubious practice” that it is. Michelle Behan has the scientific knowledge and courtroom skills necessary to challenge this and other evidentiary issue in DUI cases. Contact the Behan Law Group today.

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