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When there is a delay between a DUII arrest and a breath or blood test, the State may offer expert testimony explaining retrograde extrapolation to establish a defendant's blood alcohol content (BAC) was over the limit at the time defendant was driving.

The State appealed the trial court’s exclusion of expert testimony that Defendant’s BAC was over the legal limit of .08 when he was stopped for driving erratically, even though Defendant’s BAC was .064 – under the legal limit – at the time of the breath test, an hour and a half later. Based on the expert's calculation, called retrograde extrapolation, the expert testified that Defendant’s BAC while driving was between .08 and .10, and therefore, above the legal limit. The Court of Appeals reversed the trial court’s exclusion, holding that the expert’s testimony was admissible because it was “derived, using scientific principles, from a chemical analysis of defendant’s breath.” Defendant appealed, and the Supreme Court affirmed, holding that the State is permitted to offer the expert’s testimony explaining retrograde extrapolation to make the “necessary connection” that Defendant’s BAC was over the legal limit at the time he was driving. Affirmed.