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Can a Breath or Blood Test Be Wrong?

Their validity can be legally challenged in Massachusetts

In Massachusetts, a person is operating under the influence (OUI) if they drive a car or another motor vehicle with a blood alcohol concentration (BAC) of at least 0.08 percent. Historically, law enforcement have used breath tests or blood tests to determine BAC. But, in recent years, these tests have come under legal fire in Massachusetts over their reliability.

Breathalyzer Tests Temporarily Suspended

In January 2019, Massachusetts District Court Judge Robert Brennan declared that most breath test results were “inadmissible” in OUI cases until the commonwealth’s Office of Alcohol Testing (OAT) could complete “serious reforms, including training for staff,” and receiving accreditation from a national standards body, according to the Boston Herald. Judge Brennan’s decision was the result of the OAT’s failure “to release evidence to lawyers representing drunken driving defendants that showed around 400 Breathalyzer results were flawed.”

This decision means that, at least for the time being, Massachusetts prosecutors cannot use certain Breathalyzer test results to prove a defendant’s guilt on an OUI charge. This should not be mistaken for a complete shutdown of the commonwealth’s ability to bring—and win—such cases. In fact, breath and blood tests are just one type of evidence that can be used to prove drunk driving.

The law itself does not even require proof that a person with OUI had a BAC at or above the legal limit of 0.08 percent. The statute also defines OUI as operating a motor vehicle “while under the influence of intoxicating liquor” or other substances—including but not limited to marijuana and prescription drugs. In practice, this means police officers can arrest and charge someone with OUI based on observation as well as through certain field sobriety tests.

Understanding How Field Sobriety Tests Work

Field sobriety tests may include performing the horizontal gaze nystagmus (seeing if a suspect’s eyes jerk involuntarily while following an object from left to right), asking the suspect to walk in a straight line before turning and walking back in the opposite direction, or having the suspect stand on one leg while counting (to see if the suspect can keep balance).

Despite the fact such tests are commonplace, they are not 100 percent reliable in establishing if a person is too drunk to legally drive. A qualified Massachusetts criminal defense attorney may be able to challenge the results of a field sobriety test in court by investigating the specific facts and answering the following questions:

  • Did the suspect have a physical or mental condition that affected the outcome of the test? For example, the suspect might have had an inner ear infection, which caused her to lose balance during the standing test.
  • Did the officer administer the tests correctly? Police cannot simply make up tests on the spot. They are required to follow certain guidelines and procedures. For example, the walk-and-turn test requires a suspect to take nine steps before turning. If the officer requested, say, 10 or 12 steps, that is an incorrect procedure, and the results should not be admitted in court.
  • Was there probable cause to stop the suspect in the first place? Again, police cannot simply pull people over for no reason; there must be reasonable suspicion to initiate a traffic stop. This is lower than the probable cause standard required for arrest, but the officer must still articulate certain facts justifying the decision to administer a field sobriety test.

If you’d like more general information about DUI charges and this area of the law, see our DUI/DWI law overview.

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