An overview of field sobriety test research

Traffic officers stop moving vehicles for probable cause, most frequently a traffic code violation. When an officer approaches the driver of a stopped vehicle, he may note an odor of alcohol or other signs indicating alcohol consumption. In such circumstances, it is the officer's duty to undertake an alcohol investigation. If the driver is asked to get out of the vehicle to perform roadside maneuvers, the performance of the maneuvers, together with the officer's observations and the driver's responses to questions, are the evidence on which an arrest or release decision is based. In some jurisdictions, officers also obtain a measurement of the driver's alcohol level with a Preliminary Breath Test, but not all agencies permit breath tests at road-side or provide the instruments for them. A Standardized Field Sobriety Test battery, which includes Horizontal Gaze Nystagmus, Walk and Turn test, and One-leg Stand test, is widely used. If the driver is arrested, the admissibility of the officer's testimony about them at trial often is challenged. Sobriety tests have been examined in three laboratory studies and five field studies in the United States. Two additional studies were conducted in Finland. To provide an overview of sobriety test research in a single publication, this paper presents the methods and findings of these studies.