Zero Evidence For Zero Tolerance Pe Se Laws

At least for cannabis, that is.  Yet another study found a stunning lack of correlation between the detection of either THC or its metabolites in blood, breath, or oral fluid (saliva) and psychomotor performance, both on a driving simulator as well as on a standard field sobriety test (SFST).  While this does not mean that cannabis cannot cause impairment (it can) or that driving while high is a good idea (it's not), it does mean that the truth about cannabis and driving is far more nuanced than the prohibitionists and MADD-type zealots like to claim, and that any strict per se thresholds (let alone zero tolerance) for THC for DUI cannabis are not supported by the science.

The reason for this lack of correlation is due to the complex pharmacokinetics of cannabis, and how trace amounts of fat-soluble THC itself and especially its metabolites can linger in the body and be detected LONG after any impairment is gone.  And there is no hard and fast blood THC level threshold that can clearly (by itself) separate the actually impaired from the non-impaired, only very roughly determining how recent the last use was.  Thus unlike how it is for alcohol, chemical testing alone cannot accurately predict actual impairment for cannabis. 

That is all true whether a threshold is zero tolerance (LOD or LOQ) OR supposedly "science-based", even if the latter is slightly less ridiculous than the former.

(Even worse still are the places where driving with non-psychoactive metabolites is treated the same as THC well.  Pennsylvania, I'm looking at YOU!)

And there is still no evidence that states with strict per se laws have seen any sort of lifesaving benefits at all compared to the many states without them.

Thus, while per se laws (of any sort) make sense for alcohol, and possibly some other drugs, they make absolutely zero sense for cannabis whatsoever.  Either have an actual impairment standard alone, like many states currently do, or have that in addition to a prima facie threshold for THC (say, 5 ng/ml in blood) like Colorado currently has.  In fact, the aforementioned study found that a 2 ng/ml THC level in oral fluid did help further distinguish impairment among those who failed an SFST.  But cut out this ridiculous per se nonsense, that accomplishes literally nothing more that catching innocent sober drivers in the same dragnet along with the actually impaired.

By the way, there is actually a smartphone app called DRUID (Driving Under The Influence Of Drugs) that CAN accurately tell whether some is too messed up to drive, whether by cannabis or otherwise.  All without any sort of chemical testing whatsoever. 

It's what the late Peter McWilliams would have most likely wanted.  So what are we waiting for?