January 2013

by Nathanial Weimer, UMN Law Student, MJLST Staff

We’ve all seen the commercial. Some car comes swerving down the road, veering in and out of the proper lane and generally wreaking havoc on the neighborhood. Upon being pulled over, the driver is visibly intoxicated and the police officer quickly notices. The officer breathalyzes the driver, and if alcohol is found takes the driver back to the station for blood testing. If the driver’s blood alcohol level reaches .08, it creates a presumption that the he or she was driving under the influence of alcohol. The law enforcement process is simple and mostly effective, even if the car wasn’t actually filled with the driver’s drink of the night.

The recent passage of laws in Washington and Colorado legalizing the recreational use of marijuana will obviously increase the number of “drugged drivers” on the roads. At first glance, this might not seem like an issue–after all, police have a fairly simple method for measuring whether, and to what extent, someone is intoxicated by alcohol. Seemingly, they could employ a similar system for marijuana (driving under the influence of marijuana is, of course, still illegal). It turns out, however, that detecting the influence of marijuana presents a different set of challenges that law enforcement will have to grapple with.

The legal question for a drug DUI is whether or not one’s driving was impaired by the influence of the drug. One prominent marijuana detection method is the blood test, which measures the amount of tetrahydrocannabinol (THC), the psychoactive component in marijuana, in the blood. If some amount is found, that indicates recent use. There are problems with this test, though. First of all, THC blood levels don’t indicate the time of use because THC remains in the blood for a long period of time, according to DUI Blog. Some say it remains for days, while others claim the period can be weeks or months. Regardless, the point is that THC may be present while the effects of the drug are not; since the legal standard is impairment, a THC finding of a certain level does not necessarily meet that burden.

Effectiveness aside, blood tests also fall short from the perspective of administrative ease and individual rights. As might be expected, conducting and interpreting blood tests is time consuming and costly. As also might be expected, it’s a frustration to the driver to have to submit to a blood test taken at a police station, especially if it comes back negative. While traffic safety is clearly an important concern, well worth a few false alarms, it’s clear that a “drugged driving” detection system suffers from the lack of a breathalyzer-like device that can quickly indicate marijuana use and support blood testing of a driver.

Users, too, have a need for a short-term test that can be easily administered and understood. Drinkers of alcohol should have a general idea of their intoxication, at least up to the point where they know they should no longer drive. Most drinks have a known amount of alcohol in them, the alcohol is roughly the same strength, and there is only one way to ingest them. Marijuana on the other hand varies in strength depending on type, has multiple methods of ingestion which also vary the strength of the drug’s effect, and it’s more difficult to keep track of the amount consumed. Legal users who have ingested hours earlier and feel no effects may wonder whether their THC level is acceptable.

Technological development has provided a few solutions to the problem of short term detection. One “new” test (it is currently used in Australia and other places) is the saliva test. According to a blog on The Verge, this test is done by swabbing the driver’s mouth, can be completed within 3-5 minutes, and can measure the presence of marijuana for a few hours after ingestion. This would solve the invasiveness issue and the short-term issue. However, the amount consumed cannot be measured, and there are also accuracy based concerns–the test tends toward reporting false negatives. Still, the saliva test seems to be a promising tool for law enforcement in the future.

Another potential solution is being developed by Intelligent Fingerprinting, which is working on a fingerprint drug screening method. The device would use “high sensitivity detection reagents to identify metabolite substances in the sweat contained in fingerprints”, and would compute results in a matter of minutes. While this test would similarly fail to pinpoint the time of ingestion, or the level of impairment, it could be a very useful roadside tool. This device is still in development, however, and could still be a few years away.

With the new marijuana laws in Colorado and Washington, the pressure is on law enforcement to effectively detect drivers under the drug’s influence. While the ultimate step may be to conclusively link detection to impairment, the current step that must be taken is the development of a non-intrusive, short term device that can accurately measure a driver’s chemical levels. Possibly the saliva test will satisfy this need; possibly inventors have yet to create a viable device. In the meantime, it’s important to be careful while driving–especially if you see a car swerving like it’s in a commercial, and it’s entirely filled with smoke.