Study: Per Se Driving Limits For THC Ill Advised

  • by Paul Armentano, NORML Deputy Director May 10, 2016

    cbd_trichomesPer se driving limits for the presence of THC are arbitrary and may improperly classify motorists who are not behaviorally impaired, according to the findings of a study published today by the American Automobile Association (AAA) Foundation for Traffic Safety.

    Per se driving limits criminalize the act of operating a motor vehicle if the driver possesses detectable amounts of specific drugs or drug metabolites above a set threshold. Under these laws, drivers are guilty per se of violating the traffic safety laws even absent evidence of demonstrable behavioral impairment.

    Five states – Montana, Nevada, Ohio, Pennsylvania, and Washington – presently impose per se limits for the detection of specific amounts of THC in blood while eleven states (Arizona, Delaware, Georgia, Illinois, Indiana, Iowa, Michigan, Oklahoma, Rhode Island, Utah, and Wisconsin) impose zero tolerant per se standards. In Colorado, the presence of THC in blood above 5ng/ml “gives rise to permissible inference that the defendant was under the influence.” Legislation similar to Colorado’s law is presently pending in California.

    However, the AAA report concludes, “[A] quantitative threshold for per se laws for THC following cannabis use cannot be scientifically reported.” This is because the body metabolizes THC in a manner that is significantly distinct from alcohol. In particular, acute effects of cannabinoids lag well behind the presence of maximum THC/blood levels. Additionally, residual levels of THC may be present in blood for extended periods of time, long after any psychomotor-related effects have ceased.

    The Automobile Association’s finding is similar to that of the US National Highway Traffic Safety Administration, which acknowledges: “It is difficult to establish a relationship between a person’s THC blood or plasma concentration and performance impairing effects. … It is inadvisable to try and predict effects based on blood THC concentrations alone.”

    NORML has long articulated a similar opposition to the imposition of per se driving thresholds for THC and/or its metabolites, stating, “[R]ecently adopted statewide per se limits and zero tolerant per se thresholds in the United States criminally prohibiting the operation of a motor vehicle by persons with the trace presence of cannabinoids or cannabinoid metabolites in their blood or urine are not based upon scientific evidence or consensus. … [T]he enforcement of these strict liability standards risks inappropriately convicting unimpaired subjects of traffic safety violations, including those persons who are consuming cannabis legally in accordance with other state statutes.”

    21 responses to “Study: Per Se Driving Limits For THC Ill Advised”

    1. mexweed says:

      Assuming that THC (as I think it does) helps foster an uprush of LEAP*-memory providing a big menu of possible things you know how to do (and I consider that good), but also confusion or paranoia (alias panic) can result from not being able to decide quick enough which things among all that diversity to attend to and which ignore, therefore I agree with avoiding driving especially on FASTER traffic roads.

      But for some years I did a lot of pallet and cardboard recycling which involves SLOW driving an old pickup along alleys and slow-speed streets in industrial areas, and I think THC contributes in a positive way to that kind of driving (being ready to stop and pick up good reusable stuff for example). You can even take the kid along and get some help handing up the pallets (we stacked up to 60 on one ford f-150).

    2. mexweed says:

      LEAP: Longterm Episodic Associative Performance

    3. Matthew says:

      Are we/they talking about metabolite, or, unmetabolized THC? This is the ambiguous, billion dollar question.

      Different news sources are drawing very opposing conclusions from this AAA report, in the meantime.

      [Paul Armentano: In this instance, the substance detected was THC. However, THC may also be present for extensive periods of time (up to seven days) post-abstinence — so its detection alone provides little definitive information with regard to recency or impairment.]

    4. Julian says:

      Thanks again Paul for keeping the peer-reviewed science at the center of the discussion, and for your informative responses in Keith’s previous blog, which was about “over regulating” marijuana law, yet here we have a case of just plain misregulation. Thank God for NORML. And at least NPR gave a full report. Fuck the Today show.


      There exists no scientific way to prove upon a random traffic stop WHEN someone began metabolizing THC, much less IF they are impaired by the THC still in their blood. Scientific, peer-based review FACT, (since Mr. Armentano first published his study years before AAA backed him up Today… Get it “Today?”)

      “Today” claims “rising THC levels detected in fatal accidents”
      …without reporting whether the driver was tired or drunk, or even worse, that of COURSE there’s going to be a “recent” spike in marijuana detected in drivers BECAUSE THEIR WERE NO TESTS BEFORE THE STATE “RECENTLY” STARTED TESTING DRIVERS FOR THC IN A STATE THAT “RECENTLY” LEGALIZED MARIJUANA!!! YOU F^€*!ng IDIOTS!
      Do the editors at the Today show even CARE about how Contrived, BRIBED and disconnected from mainstream America they are? What is Kevin Sabet conducting their research? I realize of course that tabloid entertainment like Today is not where anyone should be getting their science and fact-based information, but I think even the people who watch their show have got to be calling “bull$#!+”
      At this point even the people working in private prisons, trying to patent cannabinoids or even the crooked Judge or Sherriff extorting another defendant or informant; Even THEY have to have a shred of dignity, look at these facts, turn off the Today show and say “fuck it, Im moving to Washington to go work as a marijuana legalization consultant.”

    5. Mark Mitcham says:

      I’ve said it before here, so I’ll keep it short.

      Reality Check: Driving is inherently dangerous, period. Our bodies were not evolved to take impacts at even the slowest driving speeds (and that goes for the people and animals we run over, as well.) From the first bug on your windshield to the last cat under your tire, driving is inherently violent and bloody.

      Because we, as a society, don’t respect life, all those other animals don’t count; it’s only when we start splattering human beings all over the place that we begin to notice a problem. We ask “Hey what went wrong? Geez, was it the marijuana?” No… it was the two tons of high-velocity steel, dumbass.

      I know this isn’t fun to hear, but it’s true nevertheless! I’m not making this shit up, this is reality. It’s physics vs biology.

      Look at it like this: it’s like hunting with Dick Cheney. Hunting is inherently dangerous, because it involves firearms. But hunting with Dick Cheney is even more dangerous, because he’s liquored-up and got the fire in his belly.

      So when he shoots you in the face, and you want to blame somebody or something for that, you gotta start with the fact that you were hunting, that was fundamentally dangerous. Secondly, you were hunting with Dick Cheney; that too was risky. The fact that he was three sheets to the wind definitely increases the risk, but didn’t cause or create the primary danger: buckshot.

      Driving is the same kind of thing. You can make it more dangerous, but you can’t make it safe. Don’t blame marijuana, alcohol, or anything else for that basic truth.

      • Mark Mitcham says:

        Can I offer some comic relief from my grim words?


        It’s a gutbustingly funny, deleted scene from Pineapple Express — there were several other subjects besides Private Miller in the item 9 experiment, and their recorded insights as they smoke item 9 (cannabis) will leave you in tears from laughter.

        • Julian says:

          LMAO… That brought me tears of joy, thank you brother. “I want to distrubute this in Sunday school! (Is someone playing with the thermostat?)

          Warning for first time consumers; marijuana may open your subconscious and allow you to peacefully and objectively revisit traumatic memories. Some people may experience initial paranoia followed by PTSGrowth, and your friends may feel compelled to take video and post it on you tube. All part of the healing process. 🙂

    6. Hope Humphreys says:

      If drug tests are meant to make roads safer they completely fail. They punish those whose driving may not be impaired in anyway and is unscientific. It is a law against taking drugs and not about safety, another example of the persecution of drug users.

      • mexweed says:

        Point is, the bureaucrats and paid tabloids report cannabinoid metabolite detection tests CMDT as “drug tests”, coasting along on the old dying habit of referring to cannabis as a drug rather than an herb like basil, marjoram, oregano, rosemary, sage, savory, thyme.

    7. Joseph Bonomolo says:

      Speed (not weed) kills – enough said !!!

    8. Fireweed says:

      I saw the newsblurb on this, and they ended with the comment that road fatalities have gone up significantly since legalization in those states, but didn’t cite their source.

      Here is my argument again:
      we’ve now had 20 years of some level of legalization. We’ve had 40 of some level of decriminalization. We’ve been keeping accident and fatality statistics practically since driving began.

      Could someone please crunch the numbers and get back to me on what you find? Because I’ve done several random casual samples and have found there to be an inverse relationship between permissiveness of marijuana usage and accidents and fatalities. Per capita. State by state. year by year.

      somebody please prove me wrong on this, or back me in that we already have hard evidence that pot is not a threat to highway safety.

      • Julian says:

        Let me put it like this, Fireweed; If your first child was born and the baby started crying, you would not say, “Wow! I’m experiencing a huge spike in the decibels of my baby’s voicebox!”
        Of course not, because your baby was just born, it’s it’s first time shouting through air, so there is no comparable plateau of steady data from your baby to chart a “spike” in any meaningful scientific graph analysis. There may be a control group, true, in the nursery, but no reliable data on your baby yet except that it’s crying and needs breastmilk.
        We JUST started collecting data on THC in drivers, so what we are seeing is an introduction of data that for whatever reason someone fatally crashed, whether it was texting, prescription meds or listening to Adele and falling asleep, they also happened to have some THC in their blood from whenever they consumed marijuana, whenever or even if they were impaired. But don’t believe the “spike,” when the study itself was only just born, especially if it was just born “Today.”

    9. Rod is on the gas says:

      The AAA report revealed some other stats…..

      Handsfree cell phone usage while driving increases the risk of fatal injury 4 times more than cannabis usage.

      Alcohol usage while driving increases the risk of fatal injury 15 times more than cannabis usage.

      There’s no way to get the dum-dums to quit driving while under the influence of some distraction. It’s a normal part of human behavior, even though it’s wrong.

    10. Web ber says:

      Why cant we be like switzerland in legislation.