State v. CoopermanAnnotate this Case
The State charged Defendant with driving while impaired in violation of Ariz. Rev. Stat. 28-1381(A)(1) (the (A)(1) charge) and having an alcohol concentration of .08 or more within two hours of being in physical control of a vehicle in violation of Ariz. Rev. Stat. 28-1381(A)(2). Before trial, the State moved to prevent Defendant from introducing evidence of the variability of the "partition ratio" used to convert breath alcohol concentration (AC) to blood AC readings to cast doubt on his impairment. The municipal court concluded that partition ratio evidence is relevant whenever breath test results are introduced in connection with an (A)(1) charge and denied relief. The superior court and court of appeals affirmed. The Supreme Court affirmed, holding (1) evidence relating to the variability of partition ratios in the general population is relevant to a particular defendant's state of impairment; and (2) therefore, partition ratio evidence may be admissible in a prosecution for an (A)(1) charge if the state elects to introduce breath test results to prove the defendant violated section 28-1381(A)(2).