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Statistical Evaluation of Standardized Field Sobriety Tests

NCJ Number
Journal of Forensic Sciences Volume: 50 Issue: 3 Dated: May 2005 Pages: 662-669
Michael P. Hlastala Ph.D.; Nayak L. Polissar Ph.D.; Steven Oberman J.D.
Date Published
May 2005
8 pages
This study re-evaluated previously reported conclusions regarding the accuracy of the Standardized Field Sobriety Tests (SFSTs).
SFSTs are used across the country by law enforcement officers as indicators of alcohol impairment in individuals suspected of driving while under the influence of alcohol. Their widespread and frequent use makes it crucial that they are accurately measuring what they purport to measure. In a separate study by Stuster and Burns, the accuracy of the SFSTs in predicting Blood Alcohol Concentration (BAC) was reported as 91 percent at or above 0.08 percent BAC. However, the authors posit that these conclusions were based on a heavily weighted sample of subjects with very high BAC levels. The current analysis re-evaluates the original data with a more complete statistical evaluation. The new conclusions indicate that the accuracy of the SFSTs depends on the BAC level and is much less than the 91 percent reported by Stuster and Burns. Modifications are recommended that would represent the large degree of variability of BAC in relation to SFST test scores. Modifications should include a diverse sample of BAC levels, an adjusted scoring system, and a statistically sound method for using the SFSTs to predict a BAC level greater than 0.08 percent. Figures, tables, references