‘Pot breathalyzer’ to be tested in several states this fall

If you live in Colorado, you’ve probably heard that driving while impaired by marijuana is illegal. Unfortunately, with an increasing number of states legalizing marijuana for either recreational or medical purposes, the incidence of drugged driving appears to be on the rise.

Before legalization, states defined marijuana-impaired driving as driving with any measurable amount of marijuana in your system. This was called a “per se” drugged driving law. It only made sense, however, when marijuana was illegal because the available tests could only detect that you had marijuana in your system, not whether you were actually impaired when you were driving.

As you may know, marijuana is detectible in the human body for weeks after use, even though users are only high for a couple of hours. In a state where adults can legally use marijuana, it makes no sense to penalize people for having marijuana in their systems.

What is needed is a test for actual impairment, not just the presence of the drug. Such a test has been elusive.

Now, a California company called Hound Labs believes it has developed just such a test. It’s so-called “pot breathalyzer” is operated much like an alcohol breath testing machine but can detect the presence of THC, the psychoactive component of marijuana, in the breath.

Technically, that was quite difficult to achieve. THC is perhaps a billion times less concentrated than alcohol in a user’s breath. It’s measured in parts per trillion. It took Hound Labs five years to develop a test that sensitive.

Logically, it appears to make sense that having THC in your breath would indicate that you had recently smoked it. And, the longer the time between smoking and testing, the less THC there would be to detect. However, it’s not completely clear that having THC in your breath definitively indicates impairment.

There are some potential issues. For one thing, the machine only works within a relatively narrow temperature window. It is set into an insulating base station to promote consistent results.

From a criminal defense perspective, it’s crucial that the test be both scientifically sound and technically reliable. No one should be arrested or convicted on the basis of a theory or an unreliable testing device.

Several law enforcement agencies have agreed to begin field testing the device this fall.

As it stands now, there is no particularly good way to determine if someone is driving while impaired by marijuana. We can’t just let people drive impaired, but neither can we penalize them for having used marijuana at all. An accurate, reliable “pot breathalyzer” could be a real help.

Just keep in mind that it probably won’t detect impairment from edibles.