A device which purports to provide police with a roadside device similar to a PBT (portable breath tester for alcohol) is closer to reality.

The claim of the developers is that the device can show whether a person has smoked within the previous two hours.  If that is accurate, it is likely that the device is looking for active THC (and not for urine-worthy Carboxy (THC COOH).  The COOH is what is found for days or longer in urine, having been stored in fat cells.  It is NOT psychoactive.  This device is likely intended to look for active THC (why many smoke for recreation) introduced within 2 hours or so of testing.  Obvious questions in my mind include 1) does it indicate edibles, or smoke only? 2) Does it detect vaporizer use?  3) how does mouth THC correlate to blood THC?  And REMEMBER, there is not a good correlation between blood levels of active THC and the degree of impairment or lack of impairment for a specific person.  That is different than alcohol, where there is a pretty good correlation.  One person's "go to sleep" THC blood level is another's mild buzz.

Also keep in mind that the "number" the amount of active THC in the blood does NOT tell us whether or not a person is impaired.

The above post was originally published by Lenny on TalkLeft.