With the start of legal marijuana sales just weeks away, Massachusetts law enforcement leaders are warning that police have few tools to combat stoned drivers — and little understanding of how bad the problem actually is.
On Wednesday, a new state commission tasked with studying drug-impaired driving and making recommendations to lawmakers met for the first time. The 13-member group, which includes law enforcement officials, doctors, researchers, attorneys, and civil liberties advocates, is required to submit a report to the Legislature by January.
But the commission, which will also look at driving under the influence of drugs other than marijuana, immediately ran into obstacles that have long stymied efforts to understand and combat stoned driving:
■ There’s no “Breathalyzer” for pot
While police can use a Breathalyzer to measure drunkenness, there’s no equivalent gadget for measuring how stoned a driver is.
Some researchers have promoted smartphone apps that purport to measure impairment by testing drivers’ reaction times, while others claim to have invented devices that can detect marijuana on the breath. None has been widely deployed or accepted by courts.
Blood tests can detect THC, the main psychoactive compound in cannabis, but they’re difficult to administer in the field, and it’s expensive and time consuming to bring in a suspect for testing — and in the meantime, the level of THC in the driver’s blood is dropping.
It’s even unclear whether police officers are allowed to draw blood.
“The concept of officers taking blood on the roadside raises severe civil liberties concerns,” American Civil Liberties Union field director Matt Allen said Wednesday.
■ THC doesn’t equal stoned
The presence of THC in a driver’s blood doesn’t necessarily mean the driver is impaired at that moment, just that he or she consumed the drug in recent days or weeks. Differentiating between lower and higher concentrations doesn’t help much either: One study found that even after seven days of abstinence, 24 percent of heavy cannabis users still had high levels of THC suggesting “active” impairment.
The concentration of THC “doesn’t necessarily relate to impairment,” Walpole Police Chief John Carmichael said. “We can’t make that correlation.”
For that reason, Massachusetts doesn’t have a hard threshold for marijuana-impaired driving like the 0.08 percent limit it imposes on drivers’ blood alcohol levels.
Some other states have established THC blood concentrations above which a driver is legally presumed to be high. In 12 states, that limit is zero, meaning anyone who has used the drug recently could hypothetically face operating-under-the-influence charges.
Such laws, according to New York University researcher Mark Kleiman, carry “a substantial risk of criminally punishing someone for impaired driving who was not, in fact, impaired.”
■ Questionable connection to fatal accidents
Studies have consistently found using cannabis substantially degrades driving ability and almost certainly increases the risk of fender-benders. Many marijuana users also underestimate how much marijuana can affect their driving. But the drug’s effect is far less severe than that of alcohol, and heavy users show surprising tolerance to marijuana’s impairing effects.
The presence of a link between marijuana use and the risk of getting in a fatal crash, meanwhile, is hotly disputed. One recent study by the National Highway Traffic Safety Administration found no correlation between marijuana consumption and the risk of fatal collisions, after adjusting for age and gender. Other research has produced wildly different results, depending on how impairment was measured.
But overall, marijuana use brings “only a fraction of the risks associated with driving at the legal 0.08 blood alcohol level threshold, let alone the much higher risks associated with higher levels of alcohol,” according to Kleiman, who compared the risk of driving stoned to “talking on a hands-free cellphone.”
■ Problematic field tests
Last September, the state’s highest court ruled that police officers who have not been qualified as experts cannot testify that a driver is under the influence of marijuana if the driver fails field sobriety tests, such as walking toe-to-heel, that were designed to measure alcohol impairment.
Even officers who have completed one or both of two popular national training programs for identifying drugged drivers — fewer than 2,000 officers in Massachusetts have done so — may be limited in how they can testify in court. Some judges don’t recognize the programs, and defense lawyers call them junk science.
The new commission may consider recommending the Legislature mandate courts recognize the certifications.
“Everybody wants to find the silver bullet, the equivalent of the alcohol Breathalyzer for drugs,” said John Scheft, an attorney and former prosecutor who was appointed to the drugged driving commission by Attorney General Maura Healey. “But I also think we need . . . to [look] at, what can we say right now to police officers about sobriety testing and drug recognition experts being accepted in the courts of the Commonwealth, so judges, prosecutors, defense attorneys, and the public can have a certain consistent expectation?”
■ Unclear scope of drugged driving
Massachusetts had 1,594 cases of drugged driving in 2017, according to the Registry of Motor Vehicles. But that doesn’t reflect cases still being processed, nor do numbers distinguish between cannabis and other drugs. By comparison, there were at least 6,652 drunk driving cases in 2017.Dan Adams can be reached at firstname.lastname@example.org. Follow him on Twitter @Dan_Adams86.