In order for breathalyzer results to be admissible in Massachusetts drunk driving trials, the Appeals Court has ruled that the results must be the product of what the court refers to as “proper breath test.” The Massachusetts DUI breath testing regulations specify what is required for such a breathalyzer test. According to the regulations, which were revised in 2006, a proper breath test “shall consist of a multipart procedure, involving at a minimum, the following sequence: (a) one adequate breath sample analysis, (b) one calibration standard analysis, and (c) a second adequate breath sample analysis.”
The “calibration standard analysis” is used to confirm the accuracy of the breathalyzer. In order to be approved by the Massachusetts Office of Alcohol Testing, a breathalyzer must be “capable of analyzing a reference sample of alcohol within +/0.01 blood alcohol content units of the known sample.” This means that the simulator solution sample must read.14, .15. or .16 BAC.
Also, for the breathalyzer results to be admissible to prove operating under the influence, Massachusetts law requires that the two adequate breath samples “must agree within +/-0.02 BAC.” Any difference in breath test readings greater than .02 BAC renders the breathalyzer test completely inadmissible.
In Commonwealth v. Rumery, the Massachusetts Appeals Court recently affirmed that in a drunk driving trial, the prosecution is only entitled to introduce the lower of the two breathalyzer readings, unless the OUI defendant claims that his BAC was rising after his arrest and that his BAC at the time of his driving was lower than the breathalyzer reading.
This “rising BAC defense” can sometimes be proven by using retrograde extrapolation, a scientific technique used to determining blood alcohol levels by working backwards from the time the breathalyzer is taken.
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