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Per Se Marijuana DUII Laws Are Based On Junk Science


marijuana dui duii oklahoma per seMarijuana opponents constantly try to claim that if/when marijuana becomes legal, mayhem on public roadways is sure to follow. I have yet to hear marijuana opponents back their claim up with stats, and have yet to hear them address the fact that since Colorado legalized marijuana, vehicle crash related fatalities are at an all time low. Ah, those darn pesky facts. Anyhow, as more and more states vote to legalize marijuana, more states will no doubt look into revamping their DUII laws. If they choose a per se DUII limit for marijuana, like Colorado and Washington, they will be doing so despite no solid evidence that such a policy is logical. Per The Joint Blog:

Available science fails to support the imposition of driving under the influence (DUI) impairment thresholds for cannabis in a manner that is analogous to theper se limits already in place for alcohol, according to the conclusions of a November 2014 publication published by the United States Department of Transportation, National Highway Traffic Safety Administration (NHTSA). Per setraffic safety laws criminalize those who operate a vehicle with trace or specific levels of a controlled substance in their bodily fluids, even in the absence of any further evidence indicating that the subject was behaviorally impaired.

States the paper’s authors, “Every state has enacted a law defining drivers who are at or above .08 grams per deciliter BAC as ‘legally impaired,’ but there are no similar, commonly accepted impairment levels for other drugs.” Nonetheless, despite this lack of consensus, authors acknowledge that “some state laws have established levels for some drugs at which it is illegal to operate a motor vehicle” – a position which they concede is not evidence based.

No one should consume marijuana to the point that they are high and hop in a car and drive. No responsible marijuana consumer supports the idea of driving while stoned. However, a person that consumes marijuana is not automatically too impaired to operate a motor vehicle. This is something that politicians need to realize. Establishing a per se marijuana law sets up law enforcement and prosecutors for failure, because all a person or their attorney needs to do is point out at trial that marijuana stays in one’s system for several weeks. Just because someone has cannabis in their system does not mean that they were impaired at the time they were cited for DUII.


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Johnny Green


  1. Kathleen Chippi on

    National NORML brought the unscientifc 5 nano limit to CO 3 years ago. It took 3 years and 6 times to pass. F NORML for supporting this nonsense.

  2. Study up and become an expert witness. This is going to be the next forfeiture-style abuse of power by police so you will be booked solid with court testimony.

  3. The level of THC metabolites in a person’s urine or blood has no relationship to any degree of impairment. These metabolites, unlike active THC, have no psychoactive effect and create no impairment. While cannabis intoxication may last for a couple of hours after consuming the substance, THC metabolites hang around for several days.

  4. All too true. 5 ng as objective proof of impairment is grossly foolish and not associated with reality. Somehow these legalization laws gotta get passed though. 5ng is not a show stopper for me to vote for legalization, but no provision for DUI is certainly a show stopper for a large segment of the population.

  5. I don’t see the insult nor do I mean to talk down to anyone. I don’t know what the stats are today, but the police were not arresting anyone for suspicion of driving under THC intoxication alone. If a cannabis user endangers the public by driving stoned (and I think both you and I know what I mean) or are brazenly smoking in the car, then they could and should get ticketed at the very least. People do not act responsibly, that’s why there are penalties, so I am not understanding your point. Do you believe there is much education required? “IF YOU ARE FUCKED UP FOR ANY REASON, DON’T DRIVE!” If a citizen doesn’t have that figured out, then they are not eligible for a driver’s license. After all, the Supreme Court has decided that driving is a privilege, not a right. Maybe a jail term will straighten out your attitude (I don’t mean you personally) about the responsibilities to the people around you. Before this happens:

  6. More importantly a study needs to be done on if there is a level of MJ impairment to driving. Me a retired NHTSA Crash Researcher and 42+ year lover of the magic herb should be sponsored to conduct a study. Any sponsors wanna fund me?

  7. You seemed to have forgotten about the lamestream media’s misrepresentation of the way “per se” laws are enforced in states that allow them.
    The problem with insisting that marijuana users always act responsibly and never drive impaired is about as valid as saying that someone who drinks will always stop before becoming impaired or will opt not to drive.
    The general public, at least those who do not use cannabis in any form, are typically uninformed or have acquired their info from one of the national media sources, and these reports are all over the map.
    Cordially educating the public about the effects/benefits of cannabis for various health issues will prove far more effective than constantly attempting to beat up on people who are uninformed.
    I don’t believe anyone was ever been swayed toward much of anything as a result of being insulted.

  8. Thanks for this comprehensive list. However, I think that we should just go with Cheech and Chong movies as the basis for cannabis research. Just kidding, I am bookmarking this page to have your references available.

  9. The term “junk science” was coined by climate change conspiracy theorists to write off the work by NASA, NOAA and thousands of scientists regarding the undeniable fact of climate change fueled by global warming. Now, anyone who watches Fox TV can invoke “Junk Science!” without having any idea about anything regarding a tremendously complex topic based on decades of research. I would hope that you change the subject line to avoid this meaningless, conspiracy-invoking term.
    The driving impairment level is not based on any science whatsoever. Legislators were forced to set an arbitrary blood level by voters who demanded legalization. The 5 ng level reflects their idiosyncrasies, fears and prejudices rather than objective reality and empiric evidence. The fact that THC blood levels do not correlate well to intoxication levels make objective DUI laws regarding cannabis rather complicated. The police are not charged with making subtle distinctions, they are charged with making arrests and letting you and your lawyer work it out in court. The 5ng, level, as is mentioned in other comments here, is not prima facie evidence of impairment in Colorado, but remains problematic for daily users. Don’t light up in your car and don’t drive really stoned and the odds are very low you will face DUI arrest.
    With legalization and public acceptance there will be research so that the DUI laws will be more objective. It will take time. Let us not forget that we are coming out of 70 years of vicious drug war propaganda. There are politicians, prosecutors and lobbyists like Kevin Sabet who still insist that the public was duped into legalization, they didn’t understand what they were voting for, that there is extreme “buyer remorse,” and the public must be protected by strict controls until the time they come to their senses and reinstate harsh drug laws. Once it becomes clear that there is no going back to prohibition, and legal cannabis is available to a large portion of the population, cannabis is moved from Schedule I by the Feds (I give it a 50-50 chance next year) there will be funding for research. Until that time, prohibitionists and drug warriors will continue with their strategy to block every aspect of research and debate – because they don’t like the answers.

  10. … and even though you have compiled quite a list of reviews and references, even this list is the tip of the iceberg. In all of my 60 years on this Earth, I have yet to know of someone who caused a vehicle accident as a result of having used cannabis — and that’s the truth.
    Certainly, I cannot make this claim regarding alcohol, and like probably everyone my age, we ALL know someone who has lost their life (or caused the loss of life) to an alcohol-related accident.

    This is a very lopsided argument, yet at the onset of attempting to curb cannabis use and driving, it appears that those behind the effort have grossly overreacted to testing mechanisms and procedures to keep our highways safe. It truly is not as clear-cut as some think it is, and certainly, to make the argument have even more substance, what are our present laws on the books doing about the millions of people that are on our highways under the influence of pain-killers, e.g. oxycodone and hydrocodone, to name only two? Certainly, it appears that the focus should have been here for many, many years now.

    My hope is that laws that do get passed are based not on knee-jerk actions and truly reflect that one we see as “guilty” of driving under the influence of cannabis is one that truly has created a risk to others on the highway. At present, the discussions around the levels of content of the cannabis agents in the bloodstream do NOT reflect a person creating a risk or a threat behind the wheel – they just don’t.

  11. Even if they look for active numbers, basically every true MMJ patient and anyone who smokes daily is screwed with per se DUI laws, even though we aren’t impaired.

  12. They’re taking blood and looking for active THC. It does not persist in the bloodstream like the inert metabolite does in the urine. Neither are the ng/ml anywhere near 1:1

    Colorado’s DUI-cannabis levels of active THC is not per se, it’s a rebuttable presumption. Washington is true per se. The only things the prosecutors need for conviction is the test results showing 5 ng/ml or higher and to prove that the accused was driving.

  13. Why does most everyone jump to the automatic, knee-jerk, and 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. Examples follow.

    Studies Show Marijuana Consumption Not Associated With Dangerous Driving, May Lead to Safer Drivers
    Anyone who consumes cannabis on a regular basis knows that it doesn’t make you a dangerous driver. Many people find that it makes them a safer, more focused driver; one that’s more aware of their surroundings and the dangers associated with controlling tons of gasoline-filled metal. Not only has this been an anecdotal truth for as long as cars and cannabis have been paired, science has also been clear that consuming marijuana doesn’t make you a dangerous driver, and may make some people safer drivers. More research is needed, but it’s hard to deny that of the research we have, marijuana hasn’t been found to increase a person’s risk of an accident. To back this claim up, here’s a list of studies and research conducted on this very topic, some of which were funded by national governments in hopes of different results.

    Marijuana and Driving: A Review of the Scientific Evidence
    “Marijuana has a measurable yet relatively mild effect on psychomotor skills, yet it does not appear to play a significant role in vehicle crashes, particularly when compared to alcohol. Below is a summary of some of the existing data.”

    The incidence and role of drugs in fatally injured drivers
    “There was no indication that cannabis by itself was a cause of fatal crashes.”
    REFERENCE: Washington, DC: US Department of Transportation, National Highway Traffic Safety Administration,
    Report No. DOT HS 808 065, K. Terhune. 1992.

    Marijuana’s effects on actual driving performance
    “Evidence from the present and previous studies strongly suggests that alcohol encourages risky driving whereas THC encourages greater caution. .. Drivers under the influence of marijuana retain insight in their performance and will compensate when they can, for example, by slowing down or increasing effort. As a consequence, THC’s adverse effects on driving performance appear relatively small.”
    REFERENCE: University of Adelaide study, 1995

    Role of cannabis in motor vehicle crashes
    “There is no evidence that consumption of cannabis alone increases the risk of culpability for traffic crash fatalities or injuries for which hospitalization occurs, and may reduce those risks.. The more cautious behavior of subjects who have received marijuana decreases the impact of the drug on performance, whereas the opposite holds true for alcohol.”
    REFERENCE: Marijuana: On-Road and Driving-Simulator Studies; Epidemiologic Reviews 21: 222-232, A. Smiley. 1999.

    “Both simulation and road trials generally find that driving behaviour shortly after consumption of larger doses of cannabis results in (i) a more cautious driving style; (ii) increased variability in lane position (and headway); and (iii) longer decision times. Whereas these results indicate a ‘change’ from normal conditions, they do not necessarily reflect ‘impairment’ in terms of performance effectiveness since few studies report increased accident risk.”
    REFERENCE: UK Department of Environment, Transport and the Regions (Road Safety Division). 2000.

    Cannabis And Cannabinoids – Pharmacology, Toxicology And Therapy
    “At the present time, the evidence to suggest an involvement of cannabis in road crashes is scientifically unproven”.
    REFERENCE: G. Chesher and M. Longo. 2002.

    Cannabis: Our position for a Canadian Public Policy
    “Cannabis alone, particularly in low doses, has little effect on the skills involved in automobile driving. Cannabis leads to a more cautious style of driving. However it has a negative impact on decision time and trajectory. This in itself does not mean that drivers under the influence of cannabis represent a traffic safety risk”
    REFERENCE: Canadian Senate Special Committee on Illegal Drugs. 2002.

    “The evidence to suggest an involvement of cannabis in road crashes is scientifically unproven.”
    REFERENCE: Cannabis and Cannabinoids: Pharmacology, Toxicology, and Therapeutic Potential, 2002
    Cannabis and Cannabinoids: Pharmacology, Toxicology, and Therapeutic Potential, edited by Franjo Grotenhermen, MD and Ethan Russo, MD (Haworth Press 2002).

    The Prevalence of Drug Use in Drivers, and Characteristics of the Drug-Positive Group
    “There was a clear relationship between alcohol and culpability. In contrast, there was no significant increase in culpability for cannabinoids alone.”
    REFERENCE: Accident Analysis and Prevention 32(5): 613-622. Longo, MC; Hunter, CE; Lokan, RJ; White, JM; and White, MA. (2000a).

    The Effect Of Cannabis Compared With Alcohol On Driving
    “Although cognitive studies suggest that cannabis use may lead to unsafe driving, experimental studies have suggested that it can have the opposite effect.” U.S. National Library of Medicine, 2009

    Why Medical Marijuana Laws Reduce Traffic Deaths
    “No differences were found during the baseline driving segment (and the) collision avoidance scenarios,”
    REFERENCE: Research published in the Journal of Psychoactive Drugs, 2010

    Top 10 Reasons Marijuana Users Are Safer Drivers
    “20 years of study has concluded that marijuana smokers may actually have fewer accidents than other drivers.”

    Risk of severe driver injury by driving with psychoactive substances
    “The study found that those with a blood alcohol level of 0.12% were over 30 times more likely to get into a serious accident than someone who’s consumed any amount of cannabis. .. The least risky drug seemed to be cannabis and benzodiazepines and Z-drugs.”
    REFERENCE: Accident Analysis & Prevention; Volume 59, October 2013, Pages 346–356

    Cannabis: Summary Report
    “Cannabis alone, particularly in low doses, has little effect on the skills involved in automobile driving.”
    REFERENCE: Canadian Senate Special Committee on Illegal Drugs

    Acute cannabis consumption and motor vehicle collision risk
    “There is no evidence that consumption of cannabis alone increases the risk of culpability for traffic crash fatalities or injuries for which hospitalization occurs, and may reduce those risks.”
    REFERENCE: British Medical Journal, 1999; M. Bates and T. Blakely

    Marijuana-DUI Case Tossed by Arizona Supreme Court in Metabolite Ruling
    “Because the legislature intended to prevent impaired driving, we hold that the ‘metabolite’ reference in [the law] is limited to any of a proscribed substance’s metabolites that are capable of causing impairment . . . Drivers cannot be convicted of the . . . offense based merely on the presence of a non-impairing metabolite that may reflect the prior usage of marijuana.”

    “Stick all *that* in your pipe and smoke it!”

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