Archive for July, 2006

“The Suspect’s Speech Was Slurred”

Thursday, July 6th, 2006

As with the odor of alcohol on the breath, few police reports will fail to include an observation by the arresting officer that the arrestee exhibited "slurred speech". (See my earlier post, "Alcohol on the Breath: Evidence of DUI?"). The officer fully expects to hear slurred speech in a person he suspects is intoxicated, particularly after smelling alcohol on the breath, and we tend to "hear" what we expect to hear. And hearing it supplies the officer with corroboration of his suspicions. Even assuming the honesty of the officer that the defendant?s speech was slurred, there is little evidence that this is symptomatic of intoxication.

Impairment of speech is, for example, a common — and sober — reaction to the stress, fear and nervousness that a police investigation would be expected to engender; fatigue is another well-known cause. Skeptical? Consider the following excerpt from Discover magazine:

Bartenders, police officers and hospital workers routinely identify drunks by their slurred speech. Several investigative groups judged the captain of the Exxon Valdez oil tanker to be intoxicated based solely on the sound of his voice in his radio transmissions. But a team led by Harry Holien, a phonetician at the University of Florida, has found that even self-proclaimed experts are pretty bad at estimating people?s alcohol levels by the way they talk.

Hollien asked clinicians who treat chemical dependency, along with a group of everyday people, to listen to recordings made by volunteers when they were sober, then mildly intoxicated, legally impaired, and finally, completely smashed. Listeners consistently overestimated the drunkeness of mildly intoxicated subjects. Conversely, they underestimated the alcohol levels of those who were most inebriated. Professionals were little better at perceiving the truth than the ordinary Joes….

He thinks his research could encourage police to be more wary of making snap judgments: Mild drinkers might come under needless suspicion.

Saunders, "News of Science, Medicine and Technology: Straight Talk", 21(1) Discover (Oct. 2000).

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Does Marijuana Impair Driving?

Monday, July 3rd, 2006

It is against the law to drive while under the influence of marijuana. It has always been assumed that cannabis, like alcohol, impairs the perception, coordination, reflexes and judgment necessary for the safe operation of a motor vehicle. And, of course, there have been governmental studies addressing the question: Does marijuana impair driving? Interestingly, however, the findings do not necessarily support popular opinion….

On the one hand, the California Department of Justice has found that marijuana undoubtedly impairs psychomotor abilities that are functionally related to driving and that driving skills may be impaired, particularly at high-dose levels or among inexperienced users. "Marijuana and Alcohol: A Driver Performance Study", California Office of Traffic Safety Project No. 087902 (Sept. 1986).

Contradicting these conclusions, however, are two federal studies.

The U.S. Department of Transportation conducted 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. Also, there was little evidence of interaction between alcohol and marijuana. 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.

A more recent report entitled "Marijuana and Actual Performance", DOT-HS-808-078, noted 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 study concluded that:

An important practical objective of this study was to determine whether degrees of driving impairment can be actually predicted from either measured concentration of THC in plasma or performance measured in potential roadside "sobriety" tests of tracking ability or hand and posture stability. The results, like many reported before, indicated that none of these measures accurately predicts changes in actual performance under the influence of THC…

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".

Note: "THC" stands for Delta-9-tetrahydrocannabinol, which is the intoxicating ingredient in marijuana. THC is fairly quickly converted by the body into inert metabolites, which can stay in the body for hours or even days. It is these metabolites that police blood tests in DUI arrests detect and measure. In other words, (1) marijuna may not impair driving ability at all, and (2) the blood "evidence" only measures an inactive substance which may have been there for days.

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Driving Under the Influence of…a Cell Phone

Saturday, July 1st, 2006

Now, if MADD were as interested in preventing highway deaths as they are in returning to the glory days of Prohibition….


Driving While on Cell Phone Worse

Than Driving While Drunk

THURSDAY, June 29 (Forbes) — Maneuvering through traffic while talking on the phone increases the likelihood of an accident five-fold and is actually more dangerous than driving drunk, U.S. researchers report.

That finding held true whether the driver was holding a cell phone or using a hands-free device, the researchers noted.

"As a society, we have agreed on not tolerating the risk associated with drunk driving," said researcher Frank Drews, an assistant professor of psychology at the University of Utah. "This study shows us that somebody who is conversing on a cell phone is exposing him or herself and others to a similar risk — cell phones actually are a higher risk," he said…

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