Comments on recent Appeals Court decision on the breathalyzer margin of error

The Massachusetts Court of Appeals, in the case of Commonwealth v. Rumery, decided February 4, 2011, issued a decision regarding the margin of error of the breathalyzer at Massachusetts DUI trials. The court ruled that a defendant is not entitled to a jury instruction that the breathalyzer has an inherent margin of error of .01. The defendant sought this instruction because when the Office of Alcohol testing tests a breathalyzer devise for accuracy, the machine is considered accurate as long as the machine can read a solution with a known alcohol content within a range of plus or minus .01. The court held that the .01 does not represent any specific margin of error of any particular machine. The court noted that the Commonwealth contended that the margin of error is much smaller and the court appeared to accept that finding. It is unclear how the court can accept that finding given that the Office of Alcohol Testing does not require such precision when it is testing the machine for accuracy pursuant to the periodic testing mandated by Massachusetts DUI law.

The court also stated that the margin of error has already been accounted for as a result of taking the lower of the two samples. Finally, the court held that if an instruction on a margin of error were mandated, it would require complex expert testimony on the margin of error of each machine.

In the case before the court, the defendant’s breathalyzer reading was at the legal limit of .08; accordingly, the accuracy of the machine is central to the issue as the machine is determining whether the defendant is guilty of the offense of drunk driving. The Commonwealth should be required to prove the margin of error of the machine in case with readings at or near the legal limit.

As a Massachusetts OUI attorney, this decision will not have a major impact on the defense of breathalyzer cases near the legal limit as the court only held that a jury instruction was not required. A defendant is still permitted to argue that the margin of error of the breathalyzer machine is .01 based on how the Commonwealth conducts its periodic testing. Additionally, a defense lawyer can present other evidence that impacts the margin of error of the breathalyzer machine, such as temperature, the partition ratio and individual variation in providing a breathalyzer sample, including breath volume.

As a Massachusetts DUI attorney, I have been successful in excluding breathalyzer test results from evidence in numerous case. I have had tests results as high as .20 excluded from evidence and numerous cases with reading of .16 and .15 excluded from evidence so that the jury never heard any testimony regarding a failed breathalyzer reading. There are many ways to defend a case with a breathalyzer reading of .08. It takes an experienced and dedicated lawyer to understand the science of breathalyzer testing to force the Commonwealth to prove the reliability of the result. You can call anytime to discuss your case. I typically will answer the call immediately. You can reach me at 508-455-4755 or 781-686-5924.

Contact Information