In an opinion rendered on October 26, 2009, the Massachusetts Supreme Judicial Court held that where two breath analysis tests were within less than .02 of each other, the Commonwealth could only introduce, in its prosecution of the defendant, the lower of the two breath sample results.

The decision arose from a case where a drunk driving suspect consented to breath analysis testing and the results showed a breath sample having a blood alcohol level of .09 percent at 4:14 A.M. and another breath sample having a blood alcohol level of .10 percent at 4:18 A.M.

Massachusetts law expressly requires two breath samples be taken in order to constitute a valid test. Also, if the two samples are more than .02 apart, then the test is invalid.
As an example, in the reported case, if the breath analysis results were .09 and .11, then the higher test result would be admissible. If the results were .09 and .12, the results would be invalid since the tests were more than .02 apart.

The imposition of a two-part procedure to obtain a defendant’s blood alcohol level essentially pertains to the validity of the breathalyzer test and does not speak of evidentiary value.

The Court determined that allowing both tests to be introduced at trial would unnecessarily confuse a jury on a technical matter not within their common knowledge. To otherwise permit introduction of a marginally higher breath sample result only invites jurors to do what the regulatory framework prohibits, namely, to infer, or conclude, that the lower breath sample result is not accurate and that the defendant’s blood alcohol level has been underreported.