People v. McNeal

Summary

The California Supreme Court considers whether partition-ratio evidence is admissible to rebut the statutory presumption that a defendant was under the influence in a generic DUI prosecution under Vehicle Code section 23152(a). It distinguishes the generic DUI offense from the per se DUI offense and holds that competent evidence concerning partition-ratio variability may be admitted in a generic DUI case. The court concludes that any error in excluding the evidence in this case was harmless.

Holdings

1. Competent evidence concerning variability in the 2,100-to-1 breath-to-blood partition ratio, including evidence about variability in the general population and evidence that the defendant may have had a lower ratio, is relevant and admissible in a Vehicle Code section 23152(a) prosecution when offered to rebut the section 23610 presumption that the defendant was under the influence of alcohol.
2. Partition-ratio evidence may rebut the inference of intoxication, but it may not be used to negate the basic fact triggering the section 23610 presumption or to argue that the presumption does not apply because a different ratio should have been used.
3. Any error in excluding McNeal's proposed partition-ratio evidence was harmless under the state-law prejudice standard because it was not reasonably probable that admission of the evidence would have produced a more favorable result.

Questions Presented

1. Whether evidence concerning variability in the breath-to-blood partition ratio is relevant and admissible in a generic DUI prosecution under Vehicle Code section 23152(a) to rebut the statutory presumption of intoxication under section 23610.
2. Whether partition-ratio evidence may be used to defeat or negate the operation of the section 23610 presumption by challenging the statutorily specified 2,100-to-1 ratio.
3. Whether exclusion of the proposed partition-ratio evidence required reversal of McNeal's generic DUI conviction.

Disposition

affirmed