Marijuana and Colorado DUI-D Laws

C.R.S. section 42-4-1301(1)(a) makes it a misdemeanor for any person who is under the influence of alcohol or one or more drugs, or a combination of both alcohol and one or more drugs, to drive a motor vehicle or vehicle.

C.R.S. section 42-4-1301(1)(b) makes it a misdemeanor for any person who is impaired by alcohol or by one or more drugs, or by a combination of alcohol and one or more drugs, to drive a motor vehicle or vehicle.
Marijuana, marijuana concentrate and synthetic cannabinoids all qualify as “drugs” within the meaning of this statute.

Subsection (1)(e) of this statute provides that possession of a medical marijuana license is not a defense against the charge of driving under the influence or while ability impaired. On the other hand, the driver’s mere possession of a valid medical marijuana registry identification card, “shall not, in the absence of other contributing factors, constitute probable cause for a peace officer to require the driver to submit to an analysis of his or her blood.” See subsection (6)(k).

In 2013, legislators adopted the following amendment:

(6)(a) In any prosecution for DUI or DWAI, the defendant’s BAC or drug content at the time of the commission of the alleged offense or within a reasonable time thereafter gives rise to the following presumptions or inferences:

(IV) If at such time the driver’s blood contained five nanograms or more of delta 9-tetrahydrocannabinol per milliliter in whole blood, as shown by analysis of the defendant’s blood, such fact gives rise to a permissible inference that the defendant was under the influence of one or more drugs.

There is a significant problem with the 5 nanogram delta-9 THC inference, or any inference for that matter, for marijuana intoxication. Unlike alcohol, where there are solid scientific studies to represent a correlation between blood alcohol concentration (BAC) and intoxication, measurable peak THC levels in the blood do not necessarily correlate with impairment. A person who smokes marijuana will experience the impairing effects in about 20 to 40 minutes, and the “high” rapidly dissipates around 60 minutes to 2.5 hours later—depending upon the person. However, delta-9 THC in blood will spike within the first fifteen minutes and generally fall below 5 ng within 3 hours. (Armentano, Paul, Should Per Se Limits Be Imposed for Cannabis? Equating Cannabinoid Blood Concentrations with Actual Driver Impairment: Practical Limitations and Concerns, Humboldt Journal of Social Relations, Issue 35, 2013.) Even more disturbing is that studies have found that some chronic users can have active delta-9 THC present in their blood for days after ingestion, well past when the impairing effects wear off. (Karschner et al., 2009. Do Delta- 9-tetrahydrocannabinol concentrations indicate recent use in chronic cannabis users? Addiction, 104: 2041-2048 (2009).

Concern about these issues is one of the reasons that the presumptive THC inference was not set even lower.

Unfortunately, this provision may survive a due process attack. There are two kinds of presumptions—mandatory and conclusive, and permissive. The former shifts the burden of proof or the burden of persuasion to the Defendant, which is unconstitutional in criminal cases. The latter, it has been held, supposedly shifts no burdens, but merely allows the finder of fact to find the inferred fact from the basic fact, and do not violate due process unless the inference is totally irrational. Barnes v. People, 735 P.2d 869, 872 (Colo.1987). Jolly v. People, 742 P.2d 891, 897 (Colo.1987).

Because there is arguably “some” rational connection between THC levels and impairment of driving abilities, a due process attack on the permissive inference would face an uphill battle.

Defendants should request an instruction concerning permissive inferences. At a minimum, the instruction “should tell the jury that it is not required to draw any conclusion, that any inference must be warranted by the evidence as a whole, and that the defendant has no burden to prove or disprove anything.” Jolly, supra at 898.

Colorado has a pattern jury instruction (4:13 Inferences – General), which reads as follows:
An inference permits, but does not require, you to find a fact from proof of another fact [other facts], if that conclusion is warranted by the evidence as a whole. The weight to be given the evidence rests entirely with you.

The prosecution always has the burden of proving, beyond a reasonable doubt, each element of the offense(s) charged. The defendant is presumed innocent, and has no burden to prove or disprove anything.
Defendants are entitled to present evidence in a DUID prosecution that bears upon the question of influence or impairment, and those who are frequent users of marijuana for either medical or recreational purposes may consider presenting expert testimony to rebut the inference.