DWI/DUI Based Upon Drug Metabolites

North Carolina General Statute 20-138.1, Impaired Driving, states that a person is guilty of impaired driving if he drives a vehicle on any highway, street or any public vehicular area (1) while under the influence of an impairing substance or (3) with any amount of a Schedule I controlled substance as listed in GS 90-89 or its metabolites in his blood or urine.
A metabolite is the chemical compound that is produced during the process of metabolism, that is, the breaking down of the drug by the body or the physical process of the body ridding itself of the drug.
A very interesting case was recently issued from Arizona. In State ex. Rel Montgomery v. Harris (Ariz. 2014), the Arizona Supreme Court ruled that their state’s law which prohibited driving with any illegal drugs or the metabolite must be interpreted to apply only to metabolites which are capable of causing impairment. Also, as the court in Harris pointed out, certain legal drugs share the same metabolite as illegal substances. The State must be able to show that the metabolite is actually metabolized from an illegal substance.
The Arizona case dealt with a DWI based on marijuana. The law said that if a person had illegal drugs or their metabolites, the person was deemed impaired. Unlike alcohol with the 0.08 BAC, there is no quantitative amount of a controlled substance or its metabolite to constitute impairment.
In the case of marijuana, there are two metabolites: Hydroxy-THC, the primary metabolite and Carboxy-THC, the secondary and non-impairing metabolite which can remain in the body for 28-30 days. The court ruled that the metabolite amount had to be shown to be of a sufficient quantity and character to cause actual impairment. The presence of a non-impairing metabolite reflecting prior usage was not sufficient to sustain a conviction.
Consequently, based upon wording of the NCGS, any DWI based upon a metabolite must be based upon a sufficient quantity to cause actual impairment. NCGS 20-138.1 states that any Schedule I metabolite qualifies as impairment per se. Based upon the Harris case, it can be argued that the statute must be interpreted to only apply to metabolites capable of causing impairment. Additionally, we must understand the nature of the specific drug’s metabolites to evaluate whether the primary or secondary metabolite is capable of causing impairment. Finally, the metabolite must be shown to have come from the illegal drug and not from a legal substance.
If your case is based upon a metabolite of a controlled substance, a consultation with a forensic chemist is critical to any defense.