HOW MUCH POT IS TOO MUCH WHEN DRIVING?

Recent court cases involving deaths allegedly caused by people driving
under the influence of marijuana have led to a heightened awareness
about the issue, which some sources have linked to the increasing
acceptance of medical marijuana.

In one of the cases, a California driver pleaded guilty to
manslaughter, while another driver there was found not guilty of that
charge because the effects of the drug found in his system couldn't be
proved in court.

In alcohol-related offenses, a legal blood-alcohol standard says that
any adult with more than 0.08 percent is legally drunk (lower
standards apply to minors in some states). To determine that, officers
can apply tests to drivers stopped on suspicion of OUI. Come up with
an 0.08 level or higher and you're busted, period.

But what happens when a driver has been smoking marijuana? Blood tests
can detect the weed's presence, but there are no legal standards for
how much is too much. That means it is often more difficult to make an
arrest stick in court.

And some law enforcement agencies assert that the availability of
marijuana for medicinal purposes -- and the inconsistent application
of federal laws that still make its possession and sale illegal in
most circumstances -- mean that police and prosecutors are confronting
more people who could well be one toke (or more) over the line while
on the public highways.

Medical marijuana is legal in about a third of U.S. states, including
Maine.

But lacking either a legal standard for consumption or a standardized
test for the effect of the substance in a person's system, police have
to fall back "impairment," a standard that some prosecutors say is
harder to establish in court.

Thirteen states have resolved the issue by adopting a zero-tolerance
standard -- if tests show pot use, that's a legal violation.

The rest, including Maine, make police judge impairment levels. Police
have a number of tests for that, including stability, pupil size and
the ability to estimate the passage of time.

Advocates of medicinal use say the zero-tolerance standard means
people who use pot as medicine are being penalized by being forbidden
to drive.

That could be resolved by research now under way to find an easy test
for marijuana levels in the body and for the amounts that would mean a
person is unsafe to drive. But experts say reliable tests are still
years away, and so law enforcement is still on its own.

And so are sober drivers, who deserve protection against all impaired
motorists -- no matter how they got that way.