How Do Police Test for Cannabis Intoxication?

The recreational use of cannabis has been legal in Illinois since January 1, 2020, but that doesn’t mean our state has worked out all the details. Lawmakers, law enforcement and the public are still figuring out how to deal with the issue of drugged driving.

According to one recent study, between 2013 and 2021, here was a 111% rise in the number of fatal crashes involving a driver who tested positive for cannabinoids in Illinois — from 96 in 2013 to 203 in 2021. There are multiple ways to look at this data, but many policymakers are convinced it shows a serious problem.

Drugged driving vs. drunk driving

In many ways, Illinois treats drugged driving the same way it treats drunk driving. It is against the law for anyone to operate a motor vehicle if they are under the influence of any drug that has rendered them unsafe to drive. The fact that they have used the drug legally makes no difference to this determination. Penalties for even first-time offenders can include a jail sentence of up to a year and a one-year loss of driving privileges. They get much more severe for subsequent offenses.

However, measuring intoxication can be very different depending on whether the intoxicating substance is alcohol or cannabis products.

Most of us are familiar with the so-called legal limit for drunk driving: Under Illinois law, a driver has committed per se DUI if they are found to have a blood alcohol concentration of 0.08% or higher. The legal limit is lower for certain types of drivers.

Police have several ways of measuring a driver’s BAC. One of the most common is to use a chemical breath test, such as the ones sold under the brand name Breathalyzer. The reliability of these devices is questionable, and so police often try to get a blood or urine test, both of which are considered more reliable methods. However, to get these tests, the police must generally drive a suspect to a facility where a trained professional can administer the test.

Police have various other means of gathering evidence to show that a driver was drunk. They can report that the driver had alcohol on their breath or was slurring their words. They can make the driver perform simple tasks such as walking in a straight line, and then report on how they fared.

Illinois law uses a different standard for cannabis intoxication. The so-called legal limit is 5 nanograms of THC in blood or 10 nanograms in any other bodily substance. A driver found to be over this legal limit is presumed to have committed DUI. However, Illinois does not currently recognize any cannabis equivalent to the Breathalyzer device. To measure the THC in a driver’s system, they must get a trained professional to administer a more invasive type of test. However, the police generally need probable cause to believe the person has committed a crime before they can arrest the person and bring them to a facility for a test.

As a result, police officers who suspect a driver is too high to drive may rely less on scientific tests and more on their observations of the driver’s behavior.