04 Jul 2014
As smoking marijuana is now legal, at least with a doctor’s recommendation, and at least as far as California law is considered, there has been an increase in charges of DUI Marijuana. The problem with DUI marijuana is that the tests used to determine the presence of marijuana in a person’s blood/urine are inaccurate.
DUI Marijuana is easy to charge but hard to prove.
First, these prosecutions for DUI marijuana are problematic because NO scientific literature has shown that marijuana impairs a person’s ability to drive. The results of crash fault studies fail to show that drivers with marijuana in their system are significantly more likely than drug-free drivers to be at fault in crashes.
The active ingredient in marijuana (THC or delta-9-tetrohydrocannibinal) is metabolized to 11-Hydroxy-THC or THC-OH (which is psychoactive) which can be detected in the blood, but not the urine. THC-OH is quickly metabolized to 11-nor-9-carboxy-THC or THC-COOH (non-psychoactive).
According to research, the level of THC rises to 150 ng/ml instantly after use, it then decreases to 15 ng/ml after 1 hour and 5 ng/ml at 2 hours. The THC quickly dissipates and by the time the blood is tested (after the stop, initial investigation and DRE, transport to station or hospital for blood draw) the THC is low even if the person had smoked just before driving. THC can remain at low levels for 8 hours without any measurable sign of impairment. Journal of Anal. Tox. Vol. 32: 160-164 (2008).
As with all blood tests, there are two problems: (1) a single blood test cannot predict concentration at the time of driving, the only thing that can do that is a blood test AT the time of driving; and (2) even drug concentrations at the time of driving can never predict whether a person was impaired by drugs because of the wide responses to a drug. This is a pharmacological truth and cannot be changed by crime lab personnel to obtain a criminal conviction.
Even NHTSA recognizes difficulty of DUI marijuana prosecutions. In their Drug and Human Performance Fact Sheets, they state that it is difficult to establish a relationship between a person’s THC level in blood and performance impairing effect. They acknowledge that “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 levels.”
So if you’ve been accused of DUI marijuana, it is easy to fight and win when you know the science of drug use and testing.
My article on DUI Drugs in general is here.
My article on preliminary drug testing is here.
If you have questions about DUI marijuana call me at (213) 479-5322. If you have an opinion, leave a comment.