The Answer to Cannabis DUIs is . . . Common Sense?

a marijuana leaf in front of fingerprints

Cannabis has a DUI problem.

As legal marijuana spreads across America, there remains no consistently fair or accurate manner to measure cannabis intoxication levels for drivers.

Blood tests, already slow and cumbersome to administer fully, can also be inaccurate. Unlike alcohol, which human bodies absorb pretty evenly — since its main component, ethanol, dissolves in the water in our bodies — THC dissolves in fat. Thus it is absorbed inconsistently based on the individual. A person’s weight, gender, and frequency of use can affect how long THC remains in their blood system, as can the type of cannabis product they consume.

A regular smoker may have traces of the drug in their system for up to 30 days. Someone who smokes rarely may not show traces even after immediately ingesting.

Breath tests face similar problems. Although research on the subject has come a long way, existing test kits can fail to detect incriminating levels of THC compounds even while the driver is still intoxicated.

Researchers believe a combination of breath and blood testing can together prove conclusively whether a person is intoxicated. In the meantime, what are law-enforcement officers to do?

Use their common sense, argues some cannabis regulators. If someone looks and acts intoxicated, there’s a good chance they are. If a stoned driver fails a field sobriety test, then that person is impaired, should not be behind the wheel of a vehicle, and warrants criminal charges.

After all, the point of DUIs is more to measure impairment than intoxication. If someone has consumed cannabis several hours ago, their blood test might indicate intoxication even though they could pass the field sobriety test with no problem. Do they deserve arrest? It ends up becoming the opinion of the officer.

So which is more conclusive for law enforcement? Blood tests and their potential for overstating the level of intoxication, or field sobriety tests and their risk of underrepresenting intoxication?

In a program emblematic of this issue, police officers from Colorado and Wyoming recently participated in training to recognize behavior of THC-impaired persons. A number of volunteers consumed cannabis and then interacted with these officers, including taking field sobriety tests.

The results were clear: different people showed different signs of impairment despite consuming relatively similar amount of cannabis. Those who failed the tests and demonstrated impairment would have faced arrest under normal circumstances, the officers said. Volunteers who, despite consuming cannabis, appeared normal and passed the tests would not likely have been under arrest.

The next level of technology that can prove impairment in drivers beyond a reasonable doubt remains years away at best. But legal cannabis is here now — and growing. In the meantime, regulators and law enforcement would do well to promote training among police that teaches how to recognize levels of impairment through observations and sobriety tests. Until better tech arrives, that’s likely the best bet for stopping dangerously stoned drivers: a common-sense technique that’s as effective as it gets.

Kyle Swartz is editor of Cannabis Regulator. Reach him at Read his recent piece: The Future of Cannabis Parties.