On March 16th, a 30-year-old man was spotted in a 2011 Nissan Maxima “speeding and driving recklessly” in the town of Charlton, Massachusetts. At the same time, Thomas Clardy, a police officer, husband and father of seven kids, aged 4 to 17, was parked in his patrol car in a breakdown lane.
You can guess what happened next. The Maxima swerved across the lanes of traffic and plowed into the patrol car at 81 mph. Mr. Clardy was killed. The driver of the Nissan, according to prosecutors, was “stoned behind the wheel” – high on medical marijuana[1].
With marijuana becoming legal in multiple states, and with the probability of its becoming decriminalized nationwide, the issue of marijuana intoxication is coming to the forefront.
The question is simple, and apparently very difficult to answer for everyone: When it comes to pot use, what exactly constitutes impairment?
We’ve defined the limit for blood alcohol impairment, nationwide, as 0.08% BAC (blood alcohol content). That standard seems to suit everyone.
When it comes to pot, however, things get a lot murkier.
Detecting use of pot is not all that difficult. The active ingredient in pot is tetrahydrocannabinol – or, THC. After a person uses pot, THC can be found in the blood and the saliva[2] – and there’s at least one company that is working on detecting THC using a breathalyzer[3].
The problem is not whether the individual has used marijuana; the problem is whether that person is impaired. And, as a recent study by the AAA Foundation for Traffic Safety concluded, the amount of marijuana ingestion that would cause impairment varies widely – very widely – from person to person.
Mary Wisniewski, a reporter with the Chicago Tribune, reported that the study found that “drivers can have a low level of THC, the active ingredient in marijuana, in their blood and be unsafe behind the wheel, while others with relatively high levels may not be a hazard.”[4]
States have been grappling with the issue for some time now, and the response has gone as far as a ban on any driver with any marijuana in his/her system.
The problem is that the effect of marijuana in a human being cannot be quantified in the same way as the effect of alcohol. There is too much variation from person to person, and the amount of THC in a given individual is not a reliable indicator of impairment.[5]
The question needs to be re-focused. “It’s really not about whether a person smoked a joint, took drugs or drank a few beers,” said Glenn Grant. “It’s about whether that person is impaired – no matter what the reason.”
Mr. Grant is the CEO of Atacama Resources International, which has the exclusive license to a smartphone application called Good2Drive. This app consists of a quick test developed by researchers at Stanford University. It doesn’t distinguish whether a driver is drunk, drowsy, taken drugs or smoked a joint. Rather, it measures a person’s cognitive ability and awareness, and therefore, the person’s suitability to get behind the wheel.
“When someone is drunk or stoned, and they’re getting behind the wheel of a car, the reason for that impairment is not critical," Mr. Grant continued. "What’s important is that they be stopped – immediately. They can go to an AA meeting or whatever afterwards; but the most important thing at the moment that person grabs the keys is whether he or she is fit to drive. Our app tests for that fitness.”
The existence of a standard level for marijuana use may or may not have prevented the driver of the Nissan from getting behind the wheel; but perhaps we should consider something . . . if the Nissan driver had failed the Good2Drive test and not driven that day, Mr. Clardy might still be alive.
[1] You can read a news report about the incident here: http://www.bostonherald.com/news/local_coverage/2016/05/prosecutor_driver_high_on_medical_weed_in_fatality
[2] The ABCs of Marijuana Drug Testing, NORML and the NORML Foundation, Washington DC, 2016; see: http://norml.org/marijuana/drug-testing/item/the-abcs-of-marijuana-and-drug-testing
[3] http://www.cbc.ca/news/canada/british-columbia/cannabix-technologies-testing-marijuana-breathalyzer-prototype-1.3283771
[4] Mary Wisniewski, "Legal limits for driving on pot not backed by science, study shows", The Chicago Tribune, May 10, 2016; retrieved from: http://www.chicagotribune.com/news/local/breaking/ct-marijuana-driving-study-aaa-20160509-story.html
[5] A quick Google search can bring forth a lot of information on this point, but the bottom line is, as Dr. Carl Hart wrote, "Marijuana can cause temporary impairment, and it can lower a person’s level of vigilance or focus. However, THC, the principal psychoactive chemical in marijuana, can remain in the body for up to four weeks." He also stated: "In other words, you cannot predict a person’s level of impairment based on THC levels found in their system." http://www.drcarlhart.com/marijuana-tests-dont-indicate-impairment/
