Pubdate: Thu, 09 May 2013
Source: Boulder Weekly (CO)
Column: Weed Between the Lines
Copyright: 2013 Boulder Weekly
Contact:  http://www.boulderweekly.com/
Details: http://www.mapinc.org/media/57
Author: Leland Rucker

UNDER THE INFLUENCE

Blood-Level THC Tests No Answer to Driving Safety

HB 1325, which determines driving impairment through a blood-level 
THC test, was passed by the Colorado legislature on May 7. The bill 
says anyone caught driving with more than five nanograms of THC per 
milliliter of blood is considered impaired, with the caveat that one 
could argue that you weren't impaired in court afterwards. Earlier 
versions - this is the sixth - made it an automatic conviction. Gov. 
John Hickenlooper is expected to sign the bill into law.

More than 17 million Americans admit to smoking marijuana, and in 
2010 10.6 million Americans reported driving under the influence of 
an illegal drug, with a high incidence of people age 18 to 25 among 
the respondents. More than 70 percent of those said they used 
marijuana before driving.

Eleven other states have enacted similar laws, and The Denver Post 
editorial board last week scolded Senate committee lawmakers as 
"irresponsible" for not allowing the bill to go forward earlier, 
while the Camera opined that we needed to get the five-nanogram 
blood-level test on the books quickly because "stoned people should 
not be driving."

All well and good. But there must have been reasons why lawmakers 
have been wary of using this blood test to measure marijuana driving 
impairment. Nobody wants dangerous drivers on the road. Quickly 
getting a law on the books that designates how much THC makes a 
person a dangerous driver might make some people feel more protected. 
But will it actually be making the roads, or the public, any safer?

The evidence says it won't. And that's why there was committee 
pushback. It's not because legislators don't want safe roads. It's 
that marijuana, like penicillin, or valium, or any other legal or 
illegal drug, works differently than alcohol does in the bloodstream, 
and unlike alcohol, a THC blood level is not a good indicator of intoxication.

Paul Armentano is deputy director of the National Organization for 
Reform of Marijuana Laws (NORML). His paper, "Cannabis and 
psychomotor performance: A rational review of the evidence and 
implications for public policy," was published last year. In it, 
Armentano offers four reasons why blood-level tests for marijuana can 
be suspect: 1) Peak THC blood levels do not correspond with peak 
impairment; 2) THC's effects on psychomotor performance vary widely 
among subjects; 3) Residual levels of THC can remain in the body for 
days, long beyond impairment time; 4) There is no practical method 
for blood samples to be collected on-scene.

If you consider the NORML paper pro-pot propaganda, there's the U.S. 
Department of Transportation's National Highway Traffic Safety 
Administration study of the relationship between pot and driving. Its 
conclusion in "Marijuana and Actual Driving Performance" (1993): "One 
of the program's objectives was to determine whether it is possible 
to predict driving impairment by plasma concentrations of THC and/or 
its metabolite, THC-COOH, in single samples. The answer is very 
clear: it is not."

Twenty years later, the NHTSA website continues to warn against using 
blood tests to determine THC impairment: "It is difficult to 
establish a relationship between a person's THC blood or plasma 
concentration and performance impairing effects. ... It is 
inadvisable to try and predict effects based on blood THC 
concentrations alone."

A November 2012 study, "Per Se Drugged Driving Laws and Traffic 
Fatalities" by D. Mark Anderson and Daniel I. Rees, looks at 
statistics from the 11 other states that have established laws using 
per se blood-level limits and concludes that the laws aren't 
improving traffic safety. "There is no definitive correlation between 
THC levels and behavioral impairment," the researchers wrote, "and 
there exists no evidence that imposing such standards meets their 
stated goal to improve traffic safety and reduce incidences of DUI 
drug accidents."

Apparently, lawmakers and the governor weren't persuaded by the 
science and were more interested in getting a law on the books.

As Armentano notes, Colorado has a 90 percent conviction rate in 
impaired driving cases without using blood tests, and law enforcement 
already has many tools at its disposal, including field sobriety 
tests and drug recognition training, to deal with impaired drivers.

"This is a law that is born not out of necessity, but out of 
convenience," he said. "Since November, I've been having this 
conversation almost daily, but I've yet to hear a persuasive argument 
in favor of per se testing."

Nobody wants intoxicated drivers on the road. And just because the 
science suggests that driving stoned is safer than driving drunk 
doesn't mean that responsible cannabis users should smoke and drive.

But in the face of the evidence, this law won't make our roads any safer.
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MAP posted-by: Jay Bergstrom