Michigan Debates Controversial Roadside Saliva Tests for Weed

By Paul Gaita 04/23/14

Despite bipartisan support, medical marijuana opponents and even law enforcement officials have criticized the method being proposed for testing levels of THC.

Now stick out your tongue... Shutterstock

Michigan lawmakers are throwing their weight behind a bill that would mandate police to administer saliva tests to motorists to determine whether marijuana has impaired their driving ability.

Michigan House Representative Dan Lauwers (R-Port Huron) sponsored House Bill 5385, which would require drivers suspected of reckless operation of a motor vehicle to submit to a saliva test to determine their level of impairment. As with portable breath tests for alcohol levels, failure to pass the saliva test would serve as confirming evidence for an arrest.

The bill has bipartisan support of 15 other House members, but faces considerable opposition from the more than 100,000 Michigan residents who are allowed to use medical marijuana. Advocates for medicinal marijuana use spoke out against the bill at a House Judiciary Committee meeting on April 17, prompting Lauwers to suggest an amendment that would waive the test for motorists who could show police that they possessed state medical marijuana cards.

Saliva tests for marijuana have drawn sharp criticism from the science community, law enforcement officials, and even manufacturers of the test themselves. The core of the problem is the fact that saliva testing is designed to determine the level of THC in the subject’s system. Experts like Brett Ginsburg, an associate professor at the University of Texas Health Science Center at San Antonio, note that THC is processed through the brain via the nervous system – which is unconnected to the salivary glands or saliva, resulting in an inaccurate test response. “I don’t know what the level (for impaired driving) is going to be on the Michigan tests,” said Ginsburg, “but I suspect that you’ll effectively prohibit many people from driving.”

A report from the Australian Association of Clinical Biochemists also underscored the difficulty of acquiring an accurate result from saliva tests. The authors of the report noted that while “oral fluid can provide a quick and non-invasive specimen for drug testing,” they also stated that “its collection can be thwarted by lack of available fluid due to a range of physiological factors, including drug use itself,” and can be adversely affected by food and other factors that stimulate saliva production.

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Paul Gaita lives in Los Angeles. He has contributed to the Los Angeles Times, Variety, LA Weekly, Amazon.com and The Los Angeles Beat, among many other publications and websites.