Colorado’s New Marijuana Driving Law-A Pretest for California

The new law provides that in a DUI prosecution, IF the driver’s blood contains 5 nanograms (One billionth (10-9) of a gram) or more of delta THC per milliliter in blood (based on a blood test), then a jury can be instructed as a matter of law – that this test result gives rise to a permissible inference that the driver was under the influence of drugs.This new law took many years to finally pass. The setting of the “limit” of THC in your blood by Colorado state lawmakers – provides for the threshold amount of THC of marijuana a person can have in their system and still legally drive.The new law – House Bill 1325 … says that Colorado drivers with 5 nanograms or more of THC per milliliter of blood is considered impaired to drive. THC is the psychoactive ingredient in marijuana.The level of intoxication of the alleged “stoned driver” would be determined by a blood test like the one used in Colorado DUI Cases (LINK).In the United States – only 5 states imposethresholds for cannabinoids (THC): The are – Pennsylvania (1ng/ml), Ohio (2ng/ml),Montana (5ng/ml, effective October 1, 2013), Nevada (2ng/ml) and Washington (5ng/ml). There are 10 additional states impose zero tolerance per se thresholds for the presence of cannabinoids and/or their metabolites.

What Is A Permissible Inference?This permissible inference distinction is important. In past attempts to enact this law Colorado state legislators tried to make the 5 nanogram limit standard a PER SE law as in the .08 Blood Alcohol Level (BAC) in Colorado DUI prosecutions. In DUI cases in this state, the difference between a presumption and a permissible inference is demonstrated by the language found in the DUI law itself – (for alcohol based prosecutions:)“In any prosecution for DUI or DWAI, the defendant’s Blood Alcohol Content (BAC) at the time of the commission of the alleged offense, or within a reasonable time thereafter, gives rise to the followingpresumptions or inferences:(I) If at such time the defendant’s BAC was 0.05 or less, it shall be presumed that the defendant was not under the influence of alcohol and that the defendant’s ability to operate a motor vehicle or vehicle was not impaired by the consumption of alcohol.


(III) If at such time the defendant’s BAC was 0.08 or more, such fact gives rise to the permissible inference that the defendant was under the influence of alcohol.

The new law – is a result of a compromise. The permissible inference instruction of law allows Colorado Defendants to argue in court that they weren’t impaired because the 5 nanogram limit is ONLY an indication of the ability to drive and is clearly disputable.

a new study by professor Daniel Rees of the University of Colorado and Montana State University professor D. Mark Anderson has found that “stoned-driving limits” do NOT have an impact traffic fatalities. The two profs looked at the fatality data from 16 states that have adopted marijuana-limit laws between 1990 and 2010 and their study found “no statistically significant difference between states that did and didn’t have such laws.”

Unlike Colorado’s permissible inference law – by contrast in the state of Washington a successful prosecution result is more likely for the DA because that state’s per se 5-ng limit was built into their “legalization” law. That means the jury is instructed that at the 5 nonogram level – the driver is presumed to be impaired by the THC in his or her blood.

The science underlying EITHER instruction of law is still based on scientifically challengeable studies that are flawed and attackable in court.

Even Traffic National Highway Traffic Safety Administration (NHTSA) Questions The Scientific Grounds For This Law

Interpretation of Blood Concentrations: It is difficult to establish a relationship between a person’s THC blood or plasma concentration and performance impairing effects. Concentrations of parent drug and metabolite are very dependent on pattern of use as well as dose. THC concentrations typically peak during the act of smoking, while peak 11-OH THC concentrations occur approximately 9-23 minutes after the start of smoking. Concentrations of both analytes decline rapidly and are often < 5 ng/mL at 3 hours.

Significant THC concentrations (7 to 18 ng/mL) are noted following even a single puff or hit of a marijuana cigarette. Peak plasma THC concentrations ranged from 46-188 ng/mL in 6 subjects after they smoked 8.8 mg THC over 10 minutes. Chronic users can have mean plasma levels of THC-COOH of 45 ng/mL, 12 hours after use; corresponding THC levels are, however, less than 1 ng/mL. Following oral administration, THC concentrations peak at 1-3 hours and are lower than after smoking. Dronabinol and THC-COOH are present in equal concentrations in plasma and concentrations peak at approximately 2-4 hours after dosing.

It is inadvisable to try and predict effects based on blood THC concentrations alone, and currently impossible to predict specific effects based on THC-COOH concentrations. It is possible for a person to be affected by marijuana use with concentrations of THC in their blood below the limit of detection of the method.