The Police Officer as a Drunk Driving Witness

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How effective is the officer as drunk driving witness – and specifically at detecting intoxication in DUI investigations? The general consensus, of course, is that DUI training and experience will significantly improve the ability to detect symptoms of inebriation. A study by scientists at Rutgers University's Alcohol Behavior Research Laboratory, however, questions whether officers are any better at determining if a driver is under the influence than a random juror might be. [See Langenbrucher & Nathan, Psychology, Public Policy and the Evidence for Alcohol Intoxication, American Psychologist 1070 (Oct 1983). The series of experiments was designed to test the ability of social drinkers, bartenders, and police officers to estimate the sobriety of individuals.

In the first experiment, lay witnesses were tested — 49 individuals who were characterized as "social drinkers." While these individuals watched, four test subjects — two men and two women — were "prepared" by having them consume varying amounts of alcohol until they reached different levels of blood alcohol; in some cases, no alcohol was consumed. Each subject was then brought into a room where the "witnesses" were seated and interviewed at length to obtain a range of verbal behavior and somatic and cognitive effects. The subject would then leave, his or her walking and balance under constant observation. After later reviewing the opinions of the witnesses, the scientists concluded:

The assumption that social drinkers would prove to be accurate judges of the (blood-alcohol levels) of other persons was not confirmed. On only 4 of 16 occasions did a significant number of subjects correctly classify a target on a three-stage categorical index of intoxication level. If determining whether a man is sober or intoxicated is a matter of common observation, then our subjects apparently lacked this capacity. [See Langenbrucher & Nathan, Psychology, Public Policy and the Evidence for Alcohol Intoxication, American Psychologist 1070 (Oct 1983).]

In the next experiment, the scientists considered a type of witness with more expertise in the area: bartenders. They chose 12 bartenders and then conducted the test in the familiar environment of a large hotel cocktail lounge. The results were, however, familiar:

The bartenders correctly rated a target in only one of four instances. Contrary to expectation, no relationship between years of experience as a bartender and (blood-alcohol level) estimation accuracy was found. These data suggest strongly that these bartenders did not possess and had not acquired special knowledge or skill in identifying intoxicated persons.

Finally, the psychologists turned their attention to the experts: 30 police officers from a number of New Jersey law enforcement agencies with substantial DUI experience. Fifteen of these were tested under conditions similar to those used in the first two experiments; the remaining fifteen were tested under "field conditions": at night, on roads with a driving subject who is asked to get out of the car and perform a series of field sobriety tests. The results of this experiment should be of considerable interest to any California DUI defense lawyer representing a client charged with driving under the influence of alcohol:

When police observers in the laboratory condition were compared to social drinkers who had experience an identical procedure, no difference in rating accuracy was found. Officers in the arrest analogue condition were somewhat more accurate than their colleagues in the laboratory condition but not significantly so. The scientists concluded:

The results of the three experiments described here are not reassuring. All three of the groups studied—social drinkers, bartenders, and police officers—correctly judged targets' levels of intoxication only 25 percent of the time.

The California DUI attorney should keep these studies in mind when cross-examing the "expert" officer in drunk driving cases.

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