The current battlefield in DUI prosecutions is Marijuana where states have passed per se limits of THC to establish marijuana impairment. A "per se" law imposes a presumption of impairment by a drug if any amount is detected in a urine or blood sample.
The Legal Fallacy of "Per Se" THC Laws
The truth of the matter is that blood testing is the most reliable method to determine the actual level of THC in the body. Urine tests don't show that a person has recently used marijuana, rather, depending on quantity and strength, a single dose of THC produces metabolites in urine that last for at least 12 days — long after the driving impairment effects have worn off.
The key is not to necessarily to know the exact level of THC in a driver's bloodstream, but whether or not the driver is impaired and thus incapable of safely operating a motor vehicle.It is unclear what blood level of THC constitutes actual impairment. Most credible scientists working on the issue acknowledge the difficulty of tying THC impairment to a number (in a way similar to alcohol levels in DUI cases). The risk of accidents associated with marijuana is much less conclusive than data regarding alcohol.
How Much THC Impairs?
Smoking marijuana rapidly transfers THC into the blood stream, so THC levels in the blood rise quickly. Depending on the dose, THC typically reaches peak concentrations of more than 100 ng/mL five to 10 minutes after inhalation and then rapidly decreases to between one and four ng/mL within three to four hours. However, heavy marijuana users' blood can contain detectable amounts of THC even after periods of abstention.
How Long Does it Takes to Wear Off?
In a recent study, 25% of the participants tested positive for active levels of THC after a full seven days of abstention, with the highest concentration detected being three ng/ml of whole blood. In addition, the blood serum of heavy to moderate users may contain more than two ng/mL of THC at 24 or even 48 hours after smoking a single joint, a level that studies have shown does not produce impairment.
Medical Marijuana Users
This is a big problem for medical marijuana patients who are using marijuana in compliance with state laws and their doctors' advice, but who would likely test positive for marijuana while sober.
During the debate in the Colorado Legislature over a per se THC limit of five ng/ml, Denver medical marijuana reviewer (and medical marijuana patient), William Breathes, subjected himself to blood draws to test his THC levels. After a 15-hour period of abstinence, Mr. Breathes' THC levels were still 13.5 ng/ml. According to his physician, Mr. Breathes was in no way incapacitated at the time.
This real-life account shows the very real possibility that medical marijuana patients, and other heavy marijuana users, could face criminal charges under a per se system even if they are not actually impaired.
Marijuana and Miami DUI
While Florida has not legalized medical marijuana, nor do we have a per se law regarding THC, Miami DUI Lawyer Jonathan Blecher has been defending DUI-drug impairment cases for over 30 years.
As a member of the NORML Legal Team, Miami DUI Attorney Jonathan Blecher joins in the fight to legalize medical marijuana and for sane laws about drug impairment.