November 2014

Drugged driving is becoming a serious issue.


“Describe a driver who’s high,” says Chris Haslor, a traffic safety resource prosecutor for the Colorado District Attorneys’ Council. “We ask that during our trainings, and many people make the same mistake as the general public. They think a driver who’s stoned acts the same as a driver who’s drunk. But the two are very different.”

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A flyer posted in downtown Boulder, Colorado, advertises the fact that the citizens of Colorado voted on and approved the recreational use of marijuana.

Intoxicated drivers tend to slur their words, show poor hand-eye coordination, and stumble when walking. But those who are high on marijuana can seem completely sober, Haslor notes, because the drug tends to cause more mental than physical effects, such as short-term memory loss.

For example, a classic example of a stoned driver can be seen during a field sobriety test. A driver can walk heel to toe for about nine steps, but then tends to turn around and ask, “Now, what am I supposed to be doing?”

That particular misperception is just one issue that can come up with drugged driving, Haslor says. The differences between the effects of marijuana and alcohol are creating numerous difficulties across the law enforcement and motor vehicle communities, particularly in the 23 states where medical marijuana is legal and in the states of Colorado and Washington, where marijuana has been legalized for recreational use.

Keeping an eye on how these states handle a surge in drugged driving cases is important, because it’s likely that marijuana laws will be changing in other states in the near future, Haslor believes. “Colorado and Washington are the petri dishes for legalized recreational marijuana now, but other states should get ready, because there’s a good deal of pending legislation about marijuana that indicates it could go nationwide before long,” he says.

Cause and Effect

All types of drugged driving—involving alcohol, illegal drugs or prescription drugs—are a significant problem, but marijuana is unique for a few reasons, notes Brian Ursino, director of law enforcement, AAMVA. One dominant issue is public perception.

“The general public’s attitude toward marijuana is that it’s different from other drugs,” he says. “People believe that it’s safe to use, in whatever amount they want to use it. They think that just because it’s legalized, it’s OK to drive when they’ve been using it.”

But marijuana tends to impair judgment and slows reaction times, Ursino says. It can also decrease peripheral vision and cause drivers to become confused or forgetful. When marijuana is mixed with alcohol, the effects become even more pronounced.

“One plus one doesn’t equal two when you’re talking about alcohol and marijuana, because when you use them in combination, they heighten the effect of each drug,” Ursino notes. “It’s more like one plus one equals four.”

Researchers from Columbia University’s Mailman School of Public Health studied fatal crash statistics from six states and found that a driver under the influence of alcohol is 13 times more likely to be in a fatal crash than a sober driver. A driver who has mixed alcohol and marijuana is 24 times more likely to be in a fatal crash.

If alcohol is involved, at least law enforcement officers can test intoxication levels. The same isn’t true for marijuana use. 

Even if a driver is displaying erratic driving behavior and an officer suspects marijuana use, roadside testing is very difficult. Unlike alcohol levels, which can be determined with a breathalyzer, marijuana levels can only be measured through a blood test. Because the amount of delta-9 THC (the drug’s intoxicating ingredient) begins dissipating precipitously once the user stops smoking, he or she might be at a permissible level by the time a blood test can be given at the police station.

“Basically, by the time you do the test, all your evidence is gone,” says Haslor. “That means we have to get law enforcement to look at marijuana differently, and train them to spot drugged driving more efficiently so we don’t have to rely on toxicology to bring these cases to court.”

But even when drivers are charged with driving under the influence, the challenges continue into the courtroom. Defense attorneys are adept at explaining away the type of mental lapses that come with marijuana use, Haslor says. They might say the driver was tired, for example, or simply not paying enough attention. Judges and juries tend to share public perception, too, that unless a driver is slurring his words and stumbling during the field sobriety test, he was likely “not high enough” to do any damage.

Haslor adds that juries lack a point of reference as well. For instance, most people would be familiar with the effects of six shots of tequila, but fewer know intoxication levels involved with “smoking a bowl,” and how that would lead to impaired driving.

“Right now, we’re at the very forefront of these issues,” Haslor says. “As legalized marijuana becomes more available to the general public, we’re all going to have to address these challenges of perception and enforcement.”