SAN DIEGO, Sept. 3 /PRNewswire/ — San Diego DUI lawyer Lawrence Taylor claims that California DUI laws should not be applied to marijuana usage. Unlike alcohol and many drugs, he says, marijuana probably does not impair driving.

On the one hand, the California Department of Justice has found that marijuana impairs psychomotor abilities that are functionally related to driving, particularly at high-dose levels or among inexperienced users. (”Marijuana and Alcohol: A Driver Performance Study,” California Office of Traffic Safety Project No. 087902)

However, the San Diego DUI defense attorney points out, two federal studies contradict this.

In one, the U.S. Department of Transportation conducted DUI research with a fully interactive simulator on the effects of alcohol and marijuana, alone and in combination, on driver-controlled behavior and performance. Although alcohol was found consistently and significantly to cause impairment, marijuana had only an occasional effect.

Accidents and speeding tickets reliably increased with alcohol, but no marijuana or combined alcohol-marijuana influence was noted. (”The Effects of Alcohol on Driver-Controlled Behavior in a Driving Simulator, Phase I”(DOT-HS-806-414).)

Taylor, who heads a large firm of DUI attorneys with offices in Los Angeles, San Diego, Orange County, Riverside and San Francisco, points to another more recent report. Entitled “Marijuana and Actual Performance” (DOT-HS-808-078), it also found that “THC is not a profoundly impairing drug….It apparently affects controlled information processing in a variety of laboratory tests, but not to the extent which is beyond the individual’s ability to control when he is motivated and permitted to do so in driving.”

The researchers found that it “appears not possible to conclude anything about a driver’s impairment on the basis of his/her plasma concentrations of THC and THC-COOH determined in a single sample.”

Sounds like a “whoo-hoo!” moment, huh?  Well, not so fast.  NORML’s Principles of Responsible Use states “The responsible cannabis consumer does not operate a motor vehicle or other dangerous machinery while impaired by cannabis.”

The $64,000 question*, then, is “what defines impaired?”  I can tell you that one puff off a vape bag full of Oregon’s finest will severely impair your average Kansas ditchweed smoker, while that same puff for a 5g/day Oregon patient won’t even break his concentration from completing the New York Times crossword.

The same phenomenon exists for alcohol; the alcoholic can seem perfectly capable with as many drinks under his belt as would knock out your average sorority sister.  But as a society, we decided that there should be an absolute measurable physical limit – .08 blood alcohol content – that defines impairment per se, that is, if you’re over .08 you’re too impaired even if you’re not really too impaired.

As always when there is a story about cannabis drug testing and driving, I called on NORML’s Deputy Director, Paul Armentano.  Here’s what he had to say:

As someone who is somewhat regularly brought in as a consultant for the defense in DUI-marijuana cases I can report, contrary to attorney Taylor’s claim [above], that there are in fact several available studies associating certain blood-THC levels (but not carboxy-THC levels) with psychomotor impairment and/or increased risk of traffic accident. These include:

• Drummer et al. 2004. The involvement of drugs in drivers killed in Australian road traffic crashes. Accident, Analysis and Prevention 36: 239-248.
• Grotenhermen et al. 2007. Developing per se limits for driving under cannabis. Addiction 102: 1910-1917.
• Bedard et al. 2007. The impact of cannabis on driving. Canadian Journal of Public Health 98: 6-11.
• Laumon et al. 2005. Cannabis intoxication and fatal road crashes in France: a population base case-control study. British Medical Journal 331: 1371-1377.
• Ramaekers et al. 2004. Dose related risk of motor vehicle crashes after cannabis use. Drug and Alcohol Dependence 73: 109-119.
• Khiabani et al. 2006. Relationship between THC concentration in blood and impairment in apprehended drivers. Traffic Injury Prevention 7: 111-116.

Remember that blood-THC is a measurement of the actual impairing substance (the metabolized 11-THC which is actually more psychoactive than the initial 9-THC that you inhale), while carboxy-THC (or THC-COOH) is the inactive metabolite they detect on the pee tests that doesn’t prove any impairment, only past use.

My personal preference would be that all chemical measurements of impairment, even blood-alcohol levels, be abandoned in favor of punishing people for actual impairment.  If a person is driving poorly enough to warrant a traffic stop and then cannot pass a field impairment test (walk the line, touch your nose, etc.) they should be busted for driving while impaired, no matter whether that impairment is alcohol, THC, anti-histamines, lack of sleep, or illness.

But since BAC measuring isn’t going anywhere, I suppose that we’ll have to adopt some measure of THC blood testing and some per se limit that defines impairment.  I’ll bet soon we’ll see a device like diabetics use to test blood sugar – one quick prick on the finger tip, a drop of blood on a test strip, and in 90 seconds we know what you’re on.

Related posts

• Video from California Assembly hearings on legalization of marijuana [update] (1)
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• Stash for Wed, Oct 28, 2009 (1)

This entry was posted on Friday, September 4th, 2009 at 3:36 pm and is filed under 4:20 NewsHour, Courts, Drug Testing, Science. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a trackback from your own site.