Marijuana is the most widely used drug worldwide and, after alcohol, is the most detected substance among roadside surveyed drivers. As marijuana becomes legal in more jurisdictions, this problem will continue to grow.
Marijuana intoxication leads to cognitive and psychomotor impairment resulting in altered perception, reaction time, short term memory malfunction, attention and motor skills. Marijuana has been shown to impair performance on driving simulator tasks and on open and closed driving courses for up to approximately 3 hours. Decreased car handling performance, increased reaction times, impaired time and distance estimation, inability to maintain headway, lateral travel, subjective sleepiness, motor in-coordination, and impaired sustained vigilance have all been reported.1
In many jurisdictions, law enforcement deploy drug recognition experts (DREs) at roadside to help determine marijuana impairment. DREs conduct various observational and physical tests to assess whether someone is potentially impairment and help determine the nature of such impairment. After a series of field sobriety tests, an officer may request a saliva, blood or urine sample for analysis. Despite the complex evaluation process, the opinion of a DRE is subjective and not conclusive to determine if an accused was driving a vehicle while impaired by the presence of a drug.
When a driver’s blood sample is collected, the collection almost always occurs hours after ingestion has ceased. Often, time passes between the cessation of smoking and the beginning of driving, and more time passes between the beginning of driving and the encounter with law enforcement officials. Yet more time passes between the beginning of this encounter and the point in time when blood is drawn (often after a search warrant is obtained for driving under the influence of drugs or after the driver has been transported to a hospital post-crash). Thus, the likely THC level detectable in such a blood sample will be relatively low.2
Current forms of testing for marijuana use, like blood, saliva and hair sample, can identify THC ranging from minutes to days after to actual use, making it impossible to show the difference between the two. Studies3have shown that breath is a better indicator of impairment than saliva, blood, or urine because THC is present in breath for a relatively short period of time (1-3 hours); whereas, it is excreted at detectable levels in other body fluids for many hours, days, or even weeks after smoking. This short time period of detection in breath aligns with the peak impairment window.
Cannabix is developing breathalyzer technology that would detect the presence of THC at the point of care in a non-invasive way. These kinds of tools would provide law enforcement personnel the ability to capture breath samples to help confirm the presence of marijuana when the test was administered. This kind of screening device would help officers make better decisions and vastly reduce the reliance on subjective field tests. Furthermore, it will help officers conclude whether additional (laboratory) testing is required at the police station or elsewhere.