Pubdate: Wed, 11 May 2016
Source: Minneapolis Star-Tribune (MN)
Copyright: 2016 Associated Press
Author: Joan Lowy, Associated Press


Measuring Impairment Is Ineffective, AAA Says.

Motorists are being convicted of driving under the influence of 
marijuana based on arbitrary state standards that have no connection 
to whether the driver was impaired, says a study by AAA.

The problem is growing as more states contemplate legalizing the 
drug. At least three, and possibly 11 states, will vote this fall on 
ballot measures to legalize marijuana for medicinal or recreational 
use, or both. Bills to legalize the drug have been introduced in a 
halfdozen states.

Six states - Colorado, Montana, Nevada, Ohio, Pennsylvania and 
Washington - have set specific limits for THC, the chemical in 
marijuana that makes people high, in drivers' blood. Marijuana use is 
legal in those states for either recreational or medicinal purposes, 
with the exception of Ohio. The laws presume that a driver whose THC 
level exceeds the threshold is impaired.

But the study by AAA's safety foundation says the limits have no 
scientific basis and can result in innocent drivers being convicted, 
and in guilty drivers being released.

"There is understandably a strong desire by both lawmakers and the 
public to create legal limits for marijuana impairment in the same 
manner we do alcohol," said Marshall Doney, AAA's CEO. "In the case 
of marijuana, this approach is flawed."

Another nine states, including some that have legalized marijuana for 
medical use, have zero-tolerance laws for driving and marijuana that 
make not only any presence of THC in a driver's blood illegal, but 
also the presence of its metabolites, which can linger in a driver's 
bloodstream for weeks after any impairment has dissipated.

That makes no sense, said Mark A.R. Kleiman, a New York University 
professor specializing in issues involving drugs and criminal policy. 
"A law against driving with THC in your bloodstream is not a law you 
can know you are obeying except by never smoking marijuana or never 
driving," he said.

The problem is that determining whether someone is impaired by 
marijuana, as opposed to having used the drug, is more complex than 
tests for alcohol impairment.

The degree to which a driver is impaired by marijuana use depends a 
lot on the individual, the study said. Drivers with relatively high 
levels of THC in their systems might not be impaired, while others 
with low levels may be unsafe behind the wheel.

Some drivers may be impaired when they are stopped by police, but by 
the time their blood is tested they have fallen below the threshold 
because THC dissipates rapidly. The average time to collect blood 
from a suspected driver is often more than two hours because taking a 
blood sample typically requires a warrant and transport to a police 
station or hospital.

Frequent marijuana users can exhibit persistent levels of the drug 
long after use, while THC levels decline more rapidly among occasional users.

Colorado's 5-nanogram limit for THC in blood "was picked out of thin 
air by politicians," said Robert Corry, a Denver criminal defense 
attorney. "Innocent people are convicted of DWI because of this."

Studies show that using marijuana and driving doubles the risk of a 
crash, Kleiman said. Talking on a hands-free cellphone while driving 
- - legal in all states - quadruples the crash risk, he said.
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MAP posted-by: Jay Bergstrom