The Massachusetts Appeals Court addressed the issue of proving a motorist has a blood alcohol content over .08 under the per se law when there is a substantial time lapse between the time of the breath test and driving observations. This issues frequently arises as one of the many defenses in an OUI charge with breath test results.

The Appeals Court in Commonwealth v. Dacosta recently upheld a defendant’s conviction on the “per se” charge of operating a vehicle with a BAC level of .08 or greater when the defendant’s BAC level was tested approximately an hour after the traffic stop. According to the Court, no “retrograde extrapolation” evidence was required where a breathalyzer test was administered 55 minutes after the traffic stop. To learn about the science behind retrograde extrapolation see the attached Article by Kurt Dubowski.

The defendant was stopped when an officer noticed a faulty inspection sticker on the windshield. During the stop, the officer observed that the defendant had red glassy eyes and so administered two sobriety field tests. The defendant failed both tests, and so was arrested and transported to a nearby police station.

At the station, officers administered two breathalyzer tests – one 50 minutes after the traffic stop, and the other 5 minutes later. Both tests showed a BAC level of .09. The defendant was charged with driving under the influence, as well as the per se charge of operating a motor vehicle with a BAC level of .08 or greater. The jury found the defendant guilty on only the per se charge.

After the conviction, the trial judge granted the defendant’s motion for a required finding of not guilty notwithstanding the jury verdict. The trial judge determined that it is not possible for a reasonable jury to infer the BAC level of the driver at the time he was driving from a Breathalyzer test administered an hour after he was stopped. The Appeals Court recognized that the trial judge was concerned that the driver’s BAC level may have changed between the time he was stopped and when he actually submitted to the Breathalyzer. By this reasoning, the Commonwealth would be required to submit evidence to prove that the BAC level could not have risen between those two points in time. The Appeals Court disagreed.

The concern here is that the defendant’s BAC level readings may not have accurately represented the defendant’s actual BAC level at the time of operation. A driver’s BAC level rises immediately after consumption of alcohol, prior to the alcohol’s complete absorption into the bloodstream, before the BAC level begins to fall and stabilize. This evidence leads to the argument that the defendant’s Breathalyzer readings, standing alone, were not accurate readings of the defendant’s BAC level at the time of operation. Therefore, without the Commonwealth presenting “retrograde extrapolation” evidence – mathematical computations estimating a BAC level backwards in time – the jury could not have had enough facts to find the defendant guilty on the per se charge.

Citing to its prior decisions, the Appeals Court found this argument inapplicable because the Breathalyzer were administered within a “reasonable time.” According to the Court, a Breathalyzer may be administered up to three hours after the operation of a vehicle. The three hour time period is a reasonable time frame for the defendant to be tested without the Commonwealth having to provide retrograde extrapolation evidence. The three hours allow for the officers to arrest the driver and transport him to a local police station for testing. As the defendant’s Breathalyzers were administered within one hour, the Court held that no further evidence was required to be presented to satisfy the per se charge.

Criminal prosecution involving Breathalyzer and blood sample testing can be very complicated and often requires a thorough understanding of both the law as well as the forensic science underlying the evidence.