Partition Ratio Evidence Admissible To Defend Impairment Charge Even If Prosecution Only Introduces Breath-Alcohol Test Results To Prove The Per Se Offense
State v. Cooperman (2013)
Arizona Supreme Court – Docket No. CV–12–0319–PR
The Arizona Supreme Court holds that partition ratio variability evidence (either in the general population in the individual specifically) is relevant and admissible in prosecutions for driving while impaired even if the state elects to introduce breath test results only to prove the.08 or higher per se count. The decision cited and followed Supreme Court decisions from California and Vermont on this issue.
In affirming, the Arizona Supreme Court did not address an important aspect of the Court of Appeal’s decision below in State v. Cooperman (Ariz.Ct.App. 2012) 282 P.3d 446. The lower Court additionally held that physiological variability (e.g., breathing patterns, body and breath temperatures, hematocrit levels, gender, etc.) in the general population may be admitted to cast doubt on the reliability of breath-alcohol samples in defense against both the impairment and per se charges. The California Supreme Court noted this holding in Vangelder (see below) but declined to follow it on the per se count.
EDITOR’S NOTE: NCDD member Steven Barnard contributed an amicus brief on this winning case.