Magazine article Developments in Mental Health Law

Drunk Driving: Problems with per Se Evidence

Magazine article Developments in Mental Health Law

Drunk Driving: Problems with per Se Evidence

Article excerpt

Keeping in mind that 26,300 accidental deaths are attributed to drunk driving annually in the United States, consider the following scenario: a twenty-two year old is involved in a minor motor vehicle accident, fails the field sobriety tests on two out of three items, comes before the magistrate, elects to a breath test instead of a blood test for alcohol, and tests out with a blood alcohol content (BAC) of 0.13 grams percent on the Smith and Wesson 900A breathalyzer. A well intentioned prosecutor elects to bring charges under the Virginia statute which sets 0.10 grams percent as per se evidence of intoxication. The moderately enlightened defense attorney produces witnesses who swear that the defendant t consumed the majority of his alcohol in the last few minutes prior to driving and, with the aid of an expert in alcohol kinetics, convinces the judge that it is not only possible but likely that the defendant's BAC at the time of the accident was less than 0.I0 grams percent.

Cases like this are being tried in cities and counties throughout Virginia since the implementation of the per se statute [section] 18.2-266(i) of the Virginia Code in July, 1984, which provides that:

   It shall be unlawful for any person
   to drive or operate any motor
   vehicle, engine or train (i) while
   such person has a blood alcohol
   concentration of 0.10 percent or
   more by weight by volume as
   indicated by a chemical test administered
   in accordance with the
   provisions of [section]18.2-268 ...

The flaw in this legislation rests with the time gap between the operation of the motor vehicle and the measurement of blood alcohol or breath alcohol in the driver, simply because alcohol levels rise and fall over time.

Alcohol absorption kinetics

The expected time course of blood alcohol following the ingestion of two double martinis over a twenty-minute period for a one hundred-fifty pound male is shown by the center solid line in the graph [Figure 1]. The dotted lines above and below this expected value illustrate the highest and lowest blood levels expected 95 percent of the time, known as the 95 percent confidence interval.

Alcohol is quite rapidly and reliably absorbed. About half of the absorption occurs in the stomach and the balance from the much greater surface area of the small intestine. Although concurrent ingestion of food (drinking on a full stomach) somewhat slows the rate of absorption, the fraction of alcohol absorbed will still be essentially 100 percent. On the graph, any two points chosen along the time axis from one to two hours apart show that the BAC at the time of driving, arrest, or accident may be either lower, higher, or the same as when the blood test is actually taken. Alcohol absorption is quite fast compared to the typical time interval between apprehending the driver suspected of DUI and administering a blood or breath test.

Does a low but rising blood alcohol content mean a safe driver?

We might consider this simple question from two points of view. First of all, those of us among the 80 percent of U.S. adults who do at some time drink, may well recall an early "buzz" particularly when the first drink is delivered fairly quickly into an empty stomach. This early subjective effect has correlates in laboratory studies where the more complex mental processes, cognitive functions such as decision making, are compromised early on in the oral ingestion of alcohol. In contrast, the neuromuscular or simple motor functions, such as eye-hand coordination, are compromised later as the blood alcohol content reaches its peak. There are countless decisions required for driving. The life-or-death decisions are nearly always unexpected. The decision of which way to turn to avoid hitting someone, therefore, may be faulty in the drunk driver. Cognitive functions also tend to return toward normal more quickly than neuromuscular functions as the blood alcohol level falls. …

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