The identification of alcohol intoxication by police

Background: The identification of alcohol intoxication by police, bartenders, social hosts, and potential passengers is an important issue in the prevention of alcohol-related driving accidents. This study examines the ability of police officers to correctly identify and make ratings of the sobriety of target drinkers presented on video. Methods: Raters were asked to determine (1) whether the target drinker had been drinking alcohol, (2) whether it was "okay" to serve the target another drink, and (3) whether the target drinker was "okay" to drive. A rater confidence score for each target evaluated, as well as demographic characteristics about the raters, was obtained. Results: Drinkers were accurately targeted to low (0.08-0.09%), medium (0.11-0.13%), and high (0.15-0.16%) blood alcohol concentrations (BACs) by using a method previously described. At lower BACs, most police officers were unable to identify whether or not targets had been drinking. Raters were "pretty sure" that targets in the 0.15-0.16% range had been drinking and "not sure" whether or not they should be served another drink or drive a car. Conclusions: The ability of raters to reliably identify target drinkers who were too intoxicated to drive safely was not obtained until the BACs were relatively high. These results suggest that prevention measures must focus on improving behavioral observations made of potential drunk drivers. Implications for bartenders and social hosts are discussed.