A DWI based on marijuana impairment is one of the hardest DWI cases for the state to prove. The effects of marijuana on the human body are completely distinct from the effects alcohol has on the human body. The Standardized Field Sobriety Tests that have been developed by the National Highway Traffic Safety Administration (NHTSA) do not reliably test for marijuana impairment. Many officers end up relying on non-standardized tests and observations that purportedly indicate marijuana impairment. These tests and observations, however, merely indicate the consumption of marijuana, but not impairment. Similar, chemical analysis of a person’s blood does not indicate impairment, but only indicates that the person consumed marijuana at some point. These blood tests rarely ever help the prosecution of marijuana DWIs since there is no per se impairment limit for marijuana in North Carolina like there is in other states. Even in states where there is a per se limit, the chemical properties of marijuana make it impossible to definitively say whether the amount of marijuana compounds metabolites in a person’s blood indicate any level of impairment. The marijuana that shows up in your blood could be marijuana that was smoked days or weeks before the DWI stop. Due to the severe punishments associated with a marijuana DWI, it’s important to hired a skilled and experienced Raleigh marijuana DWI attorney if you are facing charges.
Cannabis possesses a distinctive absorption pattern following ingestion. Delta-9-tetrahydrocannabinol (THC) is the primary psychoactive constituent in cannabis. Maximum levels of THC are typically present in the blood in human subjects within three to ten minutes following cannabis inhalation. However, unlike in the case of alcohol, these peak THC blood levels do not typically correspond with a subject’s maximum levels of behavioral impairment. In a clinical setting, it has been documented that subjects exhibit “little psychomotor impairment” during the initial fifteen minutes immediately following cannabis inhalation, despite maximum concentrations of THC occurring in the participants’ blood during this time period. This phenomenon is known as “counter-clockwise hysteresis,” meaning that the effects of the psychoactive substance lag behind observed, maximal drug concentrations. This is contrary to the profile of alcohol, whereby as peak blood alcohol levels positively correspond with a subject’s peak level of drug-impaired performance.
Cannabis’ maximum influence on performance typically manifests in subjects about 20 to 40 minutes following inhalation, during a time period when the subject’s THC blood levels are rapidly falling. The substance’s influence on behavior then diminishes relatively rapidly some 60 minutes to 2.5 hours after inhalation. During this period of time, subjects’ THC levels continue to decline. Because of this relatively confined duration of drug effect, it has been suggested that cannabis consumers who wish to avoid driving impaired wait a minimum of 3 to 4 hours after dosing before attempting to operate a motor vehicle.
In addition to THC, blood analyses for cannabinoids also typically screen for the additional presence of two distinct THC metabolites: hydroxy THC and carboxy THC. Hydroxy THC is psychoactive and is considered to be at least equipotent to THC. It is present in blood at low levels almost immediately following cannabis inhalation. Peak concentrations of hydroxy THC in blood are typically present some 20 to 30 minutes following inhalation. The more commonly detected cannabis metabolite in blood screens is carboxy THC. Contrary to hydroxy THC, carboxy THC is not psychoactive. Unlike hydroxy THC, carboxy THC typically remains present in blood plasma for several days in occasional users and weeks in more chronic consumers. Because this metabolite is not psychoactive and has a much longer half-life, it can neither accurately predict the time of last cannabis use nor be indicative of psychomotor performance.
Opponents of per se cannabinoid limits argue that neither the presence of cannabinoids nor their metabolites are appropriate or consistent predictors of behavioral or psychomotor impairment. They further argue that the imposition of such per se limits may result in the criminal conviction of individuals who may have previously consumed cannabis at some unspecified point in time, but were no longer under its influence. Further, cannabis’ unique pharmacokinetics and its varying effects on human performance raise questions regarding whether the imposition of such a one-size-fits-all per se limit is applicable for cannabinoids or their metabolites.
Cannabis possesses a distinctive absorption pattern following ingestion. The term pharmacokinetics refers to the process by which a drug is absorbed, distributed, metabolized, and eliminated by the body. THC concentrations typically peak during the act of smoking, while peak hydroxy-THC concentrations occur approximately 9-23 minutes after the start of smoking.
Because cannibinoids’ pharmacokinetic profile may be influence by the subjects’ prior pattern of use, as well as by the specific route of cannabis administration, rather than solely by the single use of cannabis itself, the website of the US National Highway Traffic Administration acknowledges, “It is difficult to establish a relationship between a person’s THC blood or plasma concentration and performance impairing effects.” It further concedes that concentrations of a parent drug and metabolite are very dependent on pattern of use as well as dose. On its website, NHTSA indicates that it is inadvisable to try and predict effects based on blood THC concentrations alone, and currently impossible to predict specific effects based on carboxy THC concentrations. In another article published by NHTSA, it concedes that the traces of cannabinoids can be detected in blood samples weeks after use, therefore, knowing that a driver tested positive for cannabinoids does not necessarily indicate that the person was impaired by the drug at the time of a crash.
Marijuana’s primary active chemical, THC, is absorbed and stored in fatty body tissue and due to the vary concentrations of THC, it is difficult to know the exact length of time traces are detectable in the body. Full elimination of THC can take several weeks while the peak effects of the drug appear after thirty to sixty minutes and typically last for two to four hours. For that reason, a motorist tested long after using marijuana may still test positive although the effects have long worn off. At this time, the literature attempting to associate dose-dependent blood THC concentrations with psychomotor impairment or accident risk remains limited and inconclusive. However, a driver under the age of 21 is subject to prosecution for driving with any amount of marijuana in their system. This zero tolerance policy is codified under GS 20-138.3 (Driving by person less than 21 years old after consuming alcohol or drugs).
If you have been charged with DWI based on marijuana impairment, contact our talented marijuana DWI attorneys at the Scharff Law Firm.