One of the problems with medical marijuana, at least from cops' perspective, is that pot is hard to detect in the field, and many drivers could be getting away with DUI because they're high but not drunk. Nearly one-third of fatal California crashes involve drugged drivers.

The problem inspired one California legislator to propose a law that would trigger a DUI case for anyone whose blood test shows even a trace of cannabis in their system. That could be problematic if you're a medical patient who toked yesterday but was stopped by police today. Even worse: A pot breathalyzer might be on the horizon:

Researchers in Sweden recently discovered that marijuana and even cocaine and meth could be detected by a roadside breathalyzer test. (Sort of — see more below).

See also: Marijuana: For the First Time, a Majority of Americans Say Legalize It

Not just any breathalyzer, either:

The academics from Karolinska Institute in Stockholm used a “commercially available breath sampler” called SensAbues and successfully ID'd 12 substances on the breath of some of the 40 volunteers they examined, according to a summary.

Scary, we know.

Credit: 1ncognito / Flickr

Credit: 1ncognito / Flickr

The patients had taken their fave drugs within the last 24 hours, researchers said. The filters from the tests were collected and analyzed later and — boom — they know what you did last night.

Since the detection wasn't done in the field — it appears to have taken further analysis — an instant pot detector seems a way off.

Still, this should make you potheads prepare for the day when a cop says blow and you know you're not drunk (and she does too).

Of course, there's that other, age old cannabis detector available to any officer: Their nose.

[@dennisjromero / / @LAWeeklyNews]

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