Is The Breathalyzer Really As Accurate As We Think?

In the summer of 2013, Matthew Mottor of Hinsdale, Massachusetts, met with a group of friends at the Deerfield River for a float trip and picnic. On the way to the picnic, however, Mottor was pulled over.

The officer suspected he was intoxicated and subjected him to a field breathalyzer. He blew above the legal limit on the roadside and again later at the police station on a second device.

Seems like an open and shut case, right? Not quite. Motter’s case was one of a growing number of cases that was dismissed because of questions about the accuracy of Breathalyzer test results.

“If we are going to put people in jail and punish people, take their liberties away, take their license away, we have an obligation to be accurate,” Mottor’s defense attorney, Joseph Bernard, told the New York Times.

At the heart of America’s enforcement of drunk driving laws is the breathalyzer, a technology once called the “drunkometer” and first developed in the 1950s by a police photographer and amateur chemist to enable authorities to more effectively keep impaired drivers off the road.

Early adoption was slow, but use of the device increased exponentially during the 1980s as States began to toughen up drunk driving laws in order to contain an epidemic of drunk driving accidents and fatalities.

“In most of the country, the threshold for illegal drunkenness is 0.08 grams of alcohol per 100 milliliters of blood,” according to the Times. “The only way to measure that directly is to draw blood, which requires a warrant. Breath tests are simpler.”

Since the 1980s, the results of Breathalyzer tests have been relied on by prosecutors and police as incontrovertible scientific evidence of guilt. The truth, however, is that the tests produce skewed results with alarming frequency. A 2019 investigation by the Times found that breathalyzers often produced incorrect results that were up to 40% too high. Judges in two states – New Jersey and Massachusetts – were forced to throw out over 30,000 breathalyzer tests during a recent 12-month period after determining that they were unreliable. The exclusions became among the biggest rejections of forensic science evidence in the history of the United States.

The Times found that a frequent cause of these poor results is that breathalyzers are often not calibrated correctly. Many Police departments have weak standards for maintaining the equipment and don’t have the expertise necessary to do so. Police have been caught using stale or “home-brewed” chemical solutions that distorted results. A department in Massachusetts was even found to have rats nesting inside of its breathalyzer machine. Despite this, the tests are near-universal, and every state punishes drivers in some way if they refuse to take a breathalyzer test, including Oklahoma.

“A county judge in Pennsylvania called it ‘extremely questionable’ whether any of his state’s breath tests could withstand serious scrutiny. In response, 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.’ Even some industry veterans say the machines should not be de facto arbiters of guilt.”