Although recreational marijuana is legal in Colorado, it is still illegal to drive while one’s ability is impaired. However, no test for marijuana exists that is akin to the blood alcohol content breathalyzer test. Researchers are trying to change that by experimenting with alternative tests.
Blood tests for marijuana impairment are invasive.
Currently, there is no quick or reliable method for testing marijuana impairment. Even with blood tests, there is no set amount of THC in the bloodstream that can conclusively show impairment. Marijuana can stay in the bloodstream even after its effects have worn off, which would unfairly put drivers at risk of allegations of DUI. Moreover, police officers are not equipped to perform blood tests on the street, nor should they try to do so.
Researchers are not getting what they want from breath tests.
Though some researchers have been trying to develop a device to measure THC levels on a person’s breath, it does not look like there will be a marijuana breathalyzer any time soon. Levels of THC on the breath are low, which means that any breathalyzer would be prone to error and difficult to calibrate.
THC levels in saliva are close to those found in blood.
Researchers in Texas are trying to develop a quick way to test THC content in saliva. One problem they are facing is that, since marijuana is illegal in Texas, they must use saliva samples mixed with THC; they cannot actually take saliva from people who have used marijuana. There is no telling how accurate the test will be, say, for edibles versus smoking marijuana or for distinguishing between someone who used marijuana days ago and someone under the influence.
Tests for marijuana are likely to be problematic in the future, but individuals should already be cautious of police if they use marijuana recreationally or medically. If you are stopped by a cop under suspicion of DUI, do not agree to a blood test and do not give the officer more than just identifying information before calling an attorney.