People v. Bransford

Opinion

MOSK, J.

We granted review in these consolidated matters to consider whether the trial court should have allowed defendants convicted of driving with 0.08 percent or more of alcohol in their blood to challenge *888their breath-test results by showing that their personal ratio of breath-alcohol concentration to blood-alcohol concentration (the “partition ratio”) differed from the standard partition ratio that breath-testing machines use to convert breath-alcohol readings into blood-alcohol equivalents. As will appear, we conclude the trial court correctly excluded such evidence, and we…