Have you received a lab report in a DWI case where blood is tested by the State Crime Lab for cannabinoids? If so, the report probably had a section that looked like this:
When forensic labs test blood for marijuana, they test for the presence of delta-9-tetrahydrocannabinol (THC), which is the primary psychoactive component of cannabis. Additionally, labs commonly test for two metabolites of THC (the by-products produced as the human body breaks down the THC).
The abbreviation “THCA” that the State Crime Lab uses for 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic has been a source of confusion for defense attorneys and prosecutors. This is because the abbreviation THCA is used for two different compounds: 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (an inactive metabolite of THC) and delta-9-tetrahydrocannabinolic acid (a precursor to THC found in the cannabis plant). Delta-9-tetrahydrocannabinolic acid is transformed into THC when it is heated. In much of the scientific literature on cannabis and impaired driving, 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid is abbreviated as THC-COOH, not THCA. Here are articles discussing these compounds and the confusion: here and here.
It’s no wonder that I have had defense attorneys tell me that prosecutors misinterpret the significance of the reported THCA. Prosecutors might be familiar with the THCA that is a precursor to THC because they see it reported when private labs test suspected cannabis plant material.
What does this mean for defense attorneys? Attorneys should remember that delta-9-tetrahydrocannabinol (THC) is the psychoactive component of cannabis that is most relevant to determining impairment. The THCA listed in State Crime Lab toxicology reports is not an impairing substance. It is an inactive metabolite. Attorneys should always look to the full name of the compound, not just its abbreviation to understand what substance has been identified by the lab. Finally, determining impairment isn’t as simple as looking at the amount of delta-9-tetrahydrocannabinol (THC). Check back tomorrow for additional information about marijuana and impaired driving.
Below is a chart containing the chemical structures and functions of the compounds we have discussed. Thank you to Dr. Andrew Ewens and Dr. Wilkie Wilson for their input on this post.