Saliva Test for THC Level Detection in Development

In recent years, cannabis and its derivatives having been gaining traction in the United States. Cannabis has become a serious competitor to alcohol’s long-lived reign as Americans’ recreational drug of choice. This competition primarily stems from several progressive cities and states’ decisions to relax the legal restrictions on the long-outlawed drug. Although the relaxation of laws surrounding cannabis and its byproducts results in plenty of benefits, there are drawbacks as well.

A Highway Loss Data Institute study in April of 2018 found that car crashes were up in states that had recently relaxed their laws concerning cannabis. For instance, car collisions were up as much as six percent in Colorado, Oregon, and Washington when compared with neighboring states that had not legalized the recreational use of cannabis. In an attempt to grapple with the issue, state legislators are looking into drafting laws targeting marijuana users who drive while intoxicated.

However, laws targeting stoned drivers are not as clear cut as those targeting drunk drivers. Tetrahydrocannabinol (THC), the psychoactive component of marijuana that causes intoxication, can stay in an individual’s bloodstream for days—sometimes even weeks. Alcohol, on the other hand, only stays in a person’s system for a couple of hours. Additionally, legislators have been able to create “per se” laws, or laws that punish a person for merely having a certain amount of alcohol in their system (0.08 percent BAC in all states except Utah where it is 0.05 percent BAC) regardless of intoxication level because science has proven that the per se levels correspond to the point at which a person cannot operate a vehicle as a sober person would. Since THC can stay in a person’s system well after they have sobered up, most states do not have per se laws for THC. Doing so creates the possibility that marijuana users be arrested for a DUI weeks after they have ingested the drug and well after they have sobered up from it. In other words, such laws would allow officers to arrest completely sober drivers for a DUI simply because they had THC in their system from smoking days, possibly weeks ago.

So how can law enforcement officers get an accurate measure of which drivers are THC-impaired and thus reduce collisions in the states that have legalized recreational use of the drug?

Researchers at the University of Texas, Dallas believe they have a solution. They have engineered THC sensor strips and accompanying electronic readers. The THC sensor strips contain two electrodes that are coated with an antibody that binds THC and isolates it from other compounds found in an individual’s saliva. When an individual’s saliva is put on the test strip, the strip is put into the electronic reader. A strip with THC on it rather than just normal saliva will result in a different electrical current that increases with the amount of THC in that individual’s saliva. The test takes about five minutes from start to finish, making it appealing to law enforcement for use during traffic stops. As of now, it is not clear whether the method of ingestion of THC makes a difference and how long exactly THC will remain on an individual’s tongue.

The saliva THC test is still in its early stages, but researchers say it is accurate for THC levels ranging from 100 picograms per milliliter to 100 nanograms per milliliter. One of the study’s lead researchers, Dr. Shalini Prasad, stated that preliminary clinical reports seem to suggest that one to fifteen nanograms of THC per milliliters of blood would make a driver impaired. Again, although the suggestion that a person can be impaired merely by having THC in their system may be true, the fact that a person can also still be sober while having the same levels of THC suggested by Dr. Prasad means that laws still cannot be based on THC alone without some indication of impairment as well. The hope is that this saliva test closes the gap between the mere presence of THC in a person and their intoxication from it.

While drivers have no need to worry about the saliva THC test in development at the moment, it is certainly something to keep an eye on. If the history of the breathalyzer and its rise to prominence tells us anything, the saliva THC test will soon be an important component in a law enforcement officer’s toolkits. Perhaps it will be used as frequently as breathalyzers are.

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