A former cop from British Columbia, Canada claims he has co-invented a breathalyzer that can detect if marijuana was used in the last two hours. Kal Malhi worked for law enforcement in British Columbia for ten years, four of which were spent in the drug enforcement division. Mr. Malhi is hopeful that the breathalyzer will be used by law enforcement to catch impaired drivers, and eventually also be used in the workplace to detect marijuana use. Per CTV News:
Dubbed the Cannabix Breathalyzer, Malhi's device works in a similar way to a traditional breath analyzer police officers use to test drivers suspected of operating a vehicle while inebriated. The device, which is pending a patent and still has to undergo further field testing, could potentially detect if cannabis was use within the previous two hours.
Whether or not Mr. Malhi's invention actually detects marijuana use via someone's breath will be determined by the patent process and by whether or not law enforcement decides to use it. However, even if his invention proves to work for detecting marijuana use via someone's breath, it still wont measure impairment. Just because I used marijuana two hours ago doesn't mean that I used enough to be impaired. And even if I consumed enough to be impaired two hours ago, doesn't mean I'm still impaired two hours later.
While Kal Malhi's invention is generating a buzz in the media, it's based on junk science, and is doomed to fail. The only way to determine if someone is impaired from marijuana is to do a series of field sobriety tests, and even those are not always accurate. Mr. Malhi's marijuana breathalyzer is no more helpful than a urine test, which indicates that marijuana is in someone's system, but does not automatically mean that the person was impaired at the time they were pulled over.