Noelle Phillips and Elizabeth Hernandez got some things right in their Denver Post article, “State still not sure whether legal pot made roads less safe.” The article was generally well done and reasonably accurate.
Colorado’s DUI law, which has a single definition of DUI irrespective of cause was correctly cited as a prime reason that Colorado is woefully behind in attempting to understand the impact of marijuana on road safety. If you don’t measure something, your understanding will not be based on facts. And that’s where we are today. We hope that the 2016 legislative session will begin to correct this fundamental flaw in our state’s DUI law.
Unfortunately, the Phillips and Hernandez article is rooted in the common belief that Driving Under the Influence of Drugs (DUID) is all about marijuana. It’s not. More people are killed or injured by drivers on multiple drugs than drivers on marijuana alone.
More critically, the Post article described Colorado’s 5 nanogram limit for THC as a presumption, which it’s not, contrasting it with the blood alcohol limit that affirms a driver is drunk if the blood-alcohol concentration (BAC) is more than .08 percent, which is also incorrect.
Colorado’s 5 nanogram limit is a permissible inference, not a presumption. It merely allows a court to infer that someone is driving under the influence of marijuana if other evidence supports that charge. At the same time, a 5 nanogram permissible inference effectively prevents convictions of impaired drivers who test below that arbitrary limit.
Contrary to Phillips and Hernandez’s assertion, driving with a BAC over .08 doesn’t prove that a driver is drunk, it merely proves the driver violated the DUI per se law. Colorado’s DUI statute distinguishes between DUI (the inability to drive safely) and DUI per se (driving with a BAC over .08 gm/dl). Legislators must be careful in establishing per se limits, since they have two simultaneous effects: if you’re above the limit you’re guilty, and if you’re below the limit, you’re innocent of DUI per se. A limit set too high will inappropriately exonerate impaired drivers, potentially further victimizing their victims.
Within the first hour after smoking marijuana, over 90% of the THC in blood is absorbed by the brain and other fatty tissues. It typically takes 1-3 hours after a traffic stop or a crash before blood is drawn for a drug test. As a result, laboratory tests for THC levels can never represent the THC level in the driver at the time of the infraction. This is one reason blood tests are useless for proving THC impairment, although they can be used to support charges of impairment based on other facts, including observations by trained officers.
It’s unfortunate that so many demand a scientifically valid blood THC level that serves the same purpose as the alcohol per se limit. That will never happen because the human biology of THC is vastly different than that of alcohol. This will not stop legislative efforts to establish THC per se levels, but these legislative determinations will not be supported by science.
Phillips and Hernandez used the oft-repeated refrain that, “there’s not a lot of research available.” This is nonsense. There is abundant research proving that marijuana and many other drugs impair safe driving. Lack of research is not why we have no agreed upon THC per se standard; it’s because of human biology.
I disagree with the second half of the statement attributed to Glen Davis, the Manager of Impaired Driving Programs for the Colorado Department of Transportation, “Colorado is the leader in figuring out how to prevent stoned driving and how to deal with those who do.” I doubt he even said that, since Davis knows better. How can that statement square with the litany of data shortcomings identified earlier in the Post’s article? Unlike Colorado, other states have DUI laws that distinguish between DUI-alcohol and DUID.
I testified before a legislative subcommittee, saying that Colorado has the weakest DUID laws in the nation. Colorado’s 5 ng permissible inference law makes it more difficult to convict stoned drivers than in any other state. Colorado is one of the few states in the nation where DUI is statutorily defined as “substantially incapable” of safe driving, a higher standard than used by most states.
Colorado has failed to measure the impact of legalizing and commercializing marijuana. It seems that tax revenue is the only outcome the state is interested in measuring. Perhaps the Denver Post article, as well as legislation expected to be introduced in 2016 will begin a responsible trend to measuring DUID as well, including, but not limited to DUI-marijuana.