What if my blood was not drawn within a two hour period for an Arizona DUI?

by Aaron Black • January 06, 2012

Arizona DUI law states that the blood or bodily fluid must be taken within two hours of driving. If your blood of bodily fluid was taken outside of two hours the state must present testimony from its scientist as to what the BAC level was within two hours of driving. This is called retrograde extrapolation.

Retrograde extrapolation is a scientific and mathematical process used by scientists to estimate what a person’s BAC was at a specific time based on results at a later period. With that being said retrograde extrapolation is not a trustworthy science as many assumptions are made.

In addition, the scientist must also know what and when was the last thing that you had to eat and when, what was the last thing that you had to drink. This is again another reason why you should never answer a police officers’ questions if you are arrested for a DUI.

If you are arrested for a DUI please follow the steps below

  • Always be polite with the officer
  • Provide your license, registration and insurance
  • Comply if asked to step out of your vehicle
  • If the officer asks if you have been drinking, invoke your 5th Amendment Right. Your 5th amendment right is the right to remain silent
  • Immediately request an attorney
  • Respectfully refuse all field sobriety tests such as the eye test, the walk & turn and the one leg stand
  • Refuse the preliminary breath test (PBT). This is the small breath machine that is carried by officers in their car and can be administered on the side of the road. Contrary to popular belief, your license will not be suspended if you refuse the PBT

If your blood or bodily fluid was taken outside of two hours Phoenix DUI Lawyer Aaron Black may be able to assist you. There are motions that can be filed to preclude retrograde testimony and there are defenses to be argued. Contact Phoenix DUI Attorney Aaron Black or call for a free consultation at 480-729-1683.


In light of the Coronavirus pandemic, I wanted to inform clients and potential clients I am still available for consultations. I am always available by phone, text and/or email. We can also use Facetime for social distancing. The criminal justice system is not stopping due to COVID-19.

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