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Marijuana DUI law may help convict sober drivers

By   /   May 8, 2013  /   News  /   5 Comments

DUI WHILE SOBER?: Colorado’s new stoned driving bill, HB 1325, may help to convict sober people for driving under the influence of legalized marijuana.

By Calvin Thompson | Colorado Watchdog

DENVER — After years of indecision about the legal limits of driving under the influence of marijuana, the Colorado General Assembly has finally established what counts as driving while impaired.

But critics say the legal limit is arbitrary and may result in sober drivers facing prosecution.

House Bill 1325, which passed Tuesday, is only the most recent incarnation of a “stoned driving bill.” It is the sixth and only successful attempt in the past three years; it took so long to pass because critics see it as bad science.

HB 1325 sets a similar legal standard to driving under the influence of alcohol, establishing the amount of tetrahydrocannabinol (THC) a person can have in his bloodstream before he can be considered impaired while driving. THC is the predominant psychoactive chemical found in marijuana.

According to this new standard, anyone with five nanograms or more of THC per milliliter of blood can be considered an impaired driver, and therefore guilty of a DUI. The ratio for alcohol is more lenient, at eight nanograms per milliliter of blood.

According to Mason Tvert, director of communications with the Marijuana Policy Project, this policy does not entirely reflect the scientific reality of marijuana intoxication.

“Any standards created for determining impairment as it relates to driving should be grounded in scientific evidence, but the proposed level does not appear to meet that criteria,” he wrote in a statement to Colorado Watchdog.

With the recent legalization of marijuana in Colorado and Washington, a few studies have measured the possible impairment pot can have on drivers, and the results seem to back up Tvert’s assertion.

A 2004 report by the National Highway Traffic Safety Administration revealed that is does not take much to bring a person over Colorado’s legal level. The study revealed that a single puff from a marijuana joint can be enough to elevate THC levels over three times the legal limit. THC can stay in the bloodstream in measurable quantities for hours. Furthermore, the study concludes that a great deal of impairment comes from a person’s experience with marijuana, rather than some hard, fast ratio.

“It is inadvisable to try and predict effects based on blood THC concentrations alone,” according to the NHTSA’s recommendations.

While the General Assembly just passed Colorado’s legal limit, Washington has had a similar, voter-approved restriction in effect since November, thus giving Washingtonians more time to examine repercussions from the policy.

Attorney Mark Muenster of Vancouver, Wash., has been one of the policy’s most ardent critics. In an email to the Colorado Watchdog, he explained  the legal standard of five nanograms of THC per milliliter of blood is enough to ensure that most medical marijuana users, often the most frequent users, are almost always over the legal limit.

Tvert claims the same thing will happen in Colorado.

Though it still has flaws, HB 1325 is more lenient than its predecessors. The new bill is only a “permissible inference measure,” not a “per se measure,” like many of the previous versions. In a “per se measure,” anyone passing the legal THC limit would be presumed guilty of a DUI by default. The current “permissible interference measure” means the law can simply make the case that someone is impaired if they reach the legal limit. Anyone charged with a DUI under that system can still make the case they were sober, or that THC was not affecting their driving.

While this gives sober drivers some ability to defend themselves, the law was unnecessary to begin with, Tvert said in an email. The current method of detecting marijuana DUIs is based on observing impairment in the driver’s ability, rather than blood levels. Since the current rate of marijuana DUI convictions exceeds 90 percent, Tvert argued that the most important change is that now some sober drivers will likely face conviction.

“There doesn’t appear to be a need for a new law that is likely to punish sober drivers,” he wrote in his statement.

Contact Calvin Thompson [email protected]


Calvin formerly served as staff reporter for Watchdog.org.

  • Don Johnson

    Drunks and addicts in their denial will always defend their behavior and rights no matter what laws are in place to protect the general public. Drunks and addicts while mentally impaired and disoriented under the influence, have no business driving on our public highways and creating more carnage, period!

  • Colorado remembers last week’s SC decision?

    All blood draws need warrants.

    Goes for suspected weed-DUIs too.

    Here and in its own courts the State based its case on
    an insistence that a driver who declines to submit to test­
    ing after being arrested for driving under the influence of
    alcohol {and/or weed} is always subject to a non consensual blood test
    without any precondition for a warrant. That is incorrect.”


  • AP

    Seriously. This is about someone driving NOT impaired and being penalized regardless. Even a casual smoker that has not ingested THC in a while (try a few days) will come up higher than the new “legal limit” on the amount allowed in blood. It’s asinine and not scientifically valid. Cops can pull you over for any number of things, smell weed (or say they do) on your clothes, and then submit you to a roadside test. The cops have the power, even if the person is CLEARLY NOT IMPAIRED. Drunk/impaired driving is harmful. Driving sober is NOT.

  • Justice

    When you get pulled over for a DUI or DUI-D, they give you a choice: you submit to a blood draw or automatically forfeit your license. How does that factor in?

  • Krymsun Gorean

    Why does most everyone automatically jump to the impulsive knee-jerk, FALSE assumption that cannabis impairs drivers much the same as does alcohol? Why let uninformed opinions be the basis of new laws? It took me very little time to do a search, and find actual scientific studies which indicate just how incorrect such an assumption is.

    See: http://norml.org/library/item/marijuana-and-driving-a-review-of-the-scientific-evidence

    Per Se Drugged Driving Laws and Traffic Fatalities concluded that, as currently implemented, making it illegal to operate a motor vehicle with drugs (or drug metabolites) in the system, has no discernible impact on traffic fatalities.
    See: http://ftp.iza.org/dp7048.pdf

    Driving High on Marijuana Is Safer Than Driving Drunk [ or driving sober ]
    See: http://blogs.lawyers.com/2012/04/cruising-the-high-way-safer-than-drunk-driving/

    FOR some Top Ten Reasons Marijuana Users Are Safe Drivers
    See: http://www.theweeklyconstitutional.com/news/headlines/1035-why-you-should-always-spark-up-before-hitting-the-road