Marijuana Impairment and Driving

by Ed Wood, founder of DUID Voices and resident of Colorado. The article originally appeared on the DUID Victims’ Voices Blog
Colorado’s Law is Fatally Flawed as a Measure of Marijuana Impairment

The fatal flaws of Colorado’s law regarding driving under the influence of marijuana have now come to light. Set at 5 nanograms per milliliter of blood, the 5 ng THC permissible inference law is bad. (The 5 ng law firmly positioned Colorado with the weakest DUID laws in the nation.) Colorado’s law was supposed to make it somewhat easier to convict a stoned driver of DUI if they tested at or above 5 ng/ml of THC in whole blood — while making it extremely difficult to convict a stoned driver who tested below that level.

Editor’s note– In 2013, the five nanogram limit was still part of the legislation to set a blood THC level, HB 1114, but the per se language vanished from the final bill. Instead, the text referred to “permissible inference,” which would allow people who register at five nanograms or above to present other evidence in court to prove that they weren’t actually impaired. This past week a driver in Louisiana killed 2 people on a bridge but only registered 1 ng of THC at the time of testing.

Bad LawThere are three problems with this 5 ng/ml law: First, some labs report that over 70% of stoned drivers test below 5 ng/ml THC, in part because of the long delay between first contact with a law enforcement officer and the taking of a blood sample. Some may claim that those testing below 5 ng/ml can still be prosecuted under Colorado’s impairment statute, but that claim is misleading. Such drivers cannot be successfully prosecuted, because Colorado is one of 12 states that define DUI as being “substantially incapable of safely driving,” a charge that is profoundly difficult to prove in court, even by the most gifted prosecutor.

Second, a gifted defense attorney can readily overwhelm a less-experienced county prosecutor to defeat the 5 ng permissible inference level. For example, a Colorado jury recently found Melanie Brineger not guilty of DUI after she failed her roadside Standardized Field Sobriety Test (SFST) and a subsequent laboratory found 19 ng/ml of THC in her blood.

Third, most juries, judges, and prosecutors don’t understand the differences between alcohol impairment and drug impairment. To begin with, the symptoms are markedly different. Also, most believe that marijuana is like alcohol, and that there should be a magic number of Δ9THC in a driver’s blood that will prove they are too impaired to drive safely. There is no such magic number, and if there were, it would certainly be lower than the 5 ng/ml limit established by Colorado, Washington and Montana. It would be closer to the 2 ng/ml limit established by Ohio and Nevada.
The hit-and-run driver in a six-vehicle accident in Denver on the morning of August 3 was high on both pot and alcohol. One man died, and the driver is charged with manslaughter.

The hit-and-run driver in a six-vehicle accident in Denver on the morning of August 3 was high on both pot and alcohol. A man died, and the driver is charged with manslaughter. Photo: CBS.

Difference Between Alcohol Impairment and Marijuana Impairment

While drunk drivers are most often on the road during the night time, stoned drivers are more likely to driver during the daylight.

Alcohol impairs physical abilities more than mental abilities, whereas drugs like marijuana impair mental abilities more than physical abilities. Researchers have found that current SFSTs that were designed to quantify alcohol impairment are only modestly successful in quantifying marijuana impairment (Downey et al., Psychopharmacology DOI 10.1007/s00213-012-2787-9). Since she failed her SFSTs, one must conclude that Brinegar was more than modestly impaired by marijuana, in spite of her jury’s decision.

Green Labs

Defense attorneys are now capitalizing on the Brinegar verdict, by offering “green labs” that purport to demonstrate that one can drive safely with a THC blood content greater than 5 ng/ml , ostensibly to enable more stoned drivers to escape conviction.

The purpose of using the term “green labs” is not to be cute; the term conveys to the ill-informed that these exercises are based in science. They are not. Unfortunately, there are many ill-informed in Colorado, including the legislature that passed the disastrous 5 ng bill, and those who supported its passage. All are likely to be misled.
DUID Victim Voices seeks to educate the ill-informed and welcomes help from DUID victims who wish to counteract fear and ignorance with valid science in our quest to find justice for DUID victims and to reduce drugged driving. We ask all interested DUID victims and their families to write to learn how you can help.

One thought on “Marijuana Impairment and Driving”

  1. LOL this site is just hysterical, the way you sound all serious as you spout lies and half-truths. If that man in LA only had 1 ng of THC in his system then that means that he was probably not high at the time of the accident! Meanwhile cannabis users are known to be safer drivers than completely sober drivers because they are more risk averse. (This has been proven by the same sorts of scientific studies that you have studiously avoided here on this site!)

Leave a Reply

Your email address will not be published. Required fields are marked *