A million Americans a year are arrested for drunken driving, mostly involving blowing into a device that estimates the concentration of alcohol in their blood. If the level is 0.08 or higher, they are all but certain to be convicted. Those tests often are unreliable, the New York Times reports. The technology generates skewed results with alarming frequency, even though they are marketed as precise to the third decimal place. Judges in Massachusetts and New Jersey have thrown out more than 30,000 breath tests in the past year, largely because of human errors and lax governmental oversight. Across the U.S., thousands of other tests have been invalidated in recent years.
The machines are sensitive instruments. Many haven’t been properly calibrated, yielding results that up to 40 percent too high. Maintaining machines is up to police departments that may have shoddy standards and lack expertise. Some lab officials have used stale or home-brewed chemical solutions that warped results. Experts have found serious programming mistakes in the machines’ software. States have devices that their own experts didn’t trust and have disabled safeguards meant to ensure the tests’ accuracy. A Pennsylvania judge called it “extremely questionable” whether any of his state’s breath tests could withstand serious scrutiny. Local prosecutors stopped using them. In Florida, a panel of judges described their state’s instrument as a “magic black box” with “significant and continued anomalies.” Some industry veterans say the machines should not be arbiters of guilt. “The tests were never meant to be used that way,” said John Fusco, who ran National Patent Analytical Systems, a maker of breath-testing devices. Tests from portable machines are not admissible in court in most states. They often trigger an arrest, which leads to a test on another machine at the police station. That result determines whether someone is charged.