VALIDATION OF THE STANDARDIZED FIELD SOBRIETY TEST …

1 VALIDATION OF THE STANDARDIZED FIELD SOBRIETY TESTBATTERY AT BACS BELOW PERCENTFINAL REPORTS ubmitted DEPARTMENT OF TRANSPORTATIONNATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATIONJack StusterMarcelline BurnsAugust 1998 ANACAPA SCIENCES, Box 519 Santa Barbara, California 93102--ii--[Blank Page] Technical Report Documentation Page--iii--1. Report Government Accession Recipient s Catalog HS ?4. Title and Subtitle5. Report DateValidation of the STANDARDIZED FIELD SOBRIETY Test battery atAugust 1998 BACs Below Percent7. Author(s)6. Performing Organization Code: n/aJack W. Stuster, PhD, CPE, and Marcelline Burns, PhD8. Performing Organization Report No.

2 N/a9. Performing Organization Name and Address10. Work Unit No. (TRAIS)Anacapa Sciences, Box 51911. Contract or Grant Barbara, CA 93102 DTNH22-95-C-0519212. Sponsoring Agency Name and Address13. Type of Report and Period CoveredNational Highway Traffic Safety AdministrationFinal Report400 Seventh Street, SWWashington, 2059015. Supplemental Notes14. Sponsoring Agency CodeJames F. Frank, PhD was the Contracting Officer s TechnicalRepresenative (COTR) for this AbstractThis study evaluated the accuracy of the STANDARDIZED FIELD SOBRIETY Test (SFST) battery to assist officers inmaking arrest decisions for DWI at blood alcohol concentrations (BACs) below percent.

3 NHTSA s SFST batterywas validated at percent BAC in 1981. The trend to reduce statutory DWI limits to percent BAC promptedthis research research was composed of several project tasks, including planning, site-selection, training, data entry, anddata analysis, in addition to the actual conduct of a major FIELD study. The City of San Diego, California, was selectedas the site. Seven officers of the San Diego Police Department s alcohol enforcement unit were trained in theadministration and modified scoring of NHTSA s SFST battery ( , Horizontal Gaze Nystagmus-HGN, Walk and Turn,and One Leg Stand). SFST scoring was adjusted: the observation of four HGN clues indicated a BAC percent(rather than four clues indicating a BAC percent), and the observation of two HGN clues indicated a BAC percent.

4 During routine patrols, the participating officers followed study procedures in administering SFST sand completing a data collection form for each test administered. The officers final step in each case was theadministration of an evidentiary breath alcohol analysis found the SFSTs to be extremely accurate in discriminating between BACs above and below The mean estimated and measured BACs of the 297 motorists tested were and , respectively;the difference between the means ( percent BAC) is very small and operationally irrelevant. Further, analysesfound the HGN test to be the most predictive of the three components of the SFST battery (r= ), however ahigher correlation was obtained when the results of all three tests were combined (r= ).

5 Decision analyses found that officers estimates of whether a motorist s BAC was above or below or were extremely accurate. Estimates at the level were accurate in 91 percent of the cases, or as high as94 percent if explanations for some of the false positives are accepted. Officers estimates of whether a motorist sBAC was above percent but lower than percent were accurate in 94 percent of the decisions to arrest andin 80 percent of cases overall. Also, the officers and prosecutors who were interviewed about the SFSTs found thetest battery to be acceptable for FIELD use to establish probable cause for DWI results of this study provide clear evidence of the validity of the STANDARDIZED FIELD SOBRIETY Test battery todiscriminate at percent BAC, using a slightly modified scoring procedure.

6 Further, study results stronglysuggest that the SFSTs also accurately discriminate at percent Key Words18. Distribution StatementDWI, DUI, detection, FIELD SOBRIETY , performance tests ,alcohol, law enforcement, highway safety19. Security Classif. (of this report)20. Security Classif. (of this page)21. No. of Pages22. PriceUnclassifiedUnclassified-- iv --[Blank Page] Final ReportValidation of the SFST battery at BACs Below Percent-- v --EXECUTIVE SUMMARYThis report documents the research activities and presents the results of astudy conducted for the National Highway Traffic Safety Administration (NHTSA)to evaluate the accuracy of the STANDARDIZED FIELD SOBRIETY Test (SFST) battery toassist officers in making arrest decisions and to discriminate blood alcoholconcentrations (BACs) below percent.

7 NHTSA s SFST battery was validated percent BAC in 1981. The trend to reduce statutory DWI limits to percentBAC prompted this research project. DESCRIPTION OF THE RESEARCHThe research was composed of several project tasks, including planning, site-selection, training, data entry, and data analysis, in addition to the actual conduct ofa major FIELD study. The City of San Diego, California, was selected as the site of thefield study. Seven officers of the San Diego Police Department s alcohol enforcementunit were trained in the administration and modified scoring of NHTSA s SFST battery ( , Horizontal Gaze Nystagmus, Walk and Turn, and One Leg Stand).

8 SFST scoring was changed slightly: the observation of four horizontal gaze nystagmus(HGN) clues indicated a BAC percent (rather than four clues indicating a BAC percent), and the observation of two HGN clues indicated a BAC routine patrols, the participating officers followed study procedures inadministering SFSTs and completing a data collection form for each testadministered during the study period. The officers final step in each case was theadministration of an evidentiary breath alcohol participating officers completed a total of 298 data collection forms; onlyone case was eliminated from analysis because the motorist refused all forms ofBAC testing.

9 Data analysis found the SFSTs to be extremely accurate indiscriminating between BACs above and below percent. The mean estimatedand measured BACs of the 297 motorists tested were and , respectively;the difference between the means ( percent BAC) is very small andoperationally irrelevant. Further, analyses found the HGN test to be the mostpredictive of the three components of the SFST battery (r= ), however a highercorrelation was obtained when the results of all three tests were combined (r= ).The results of decision analyses provide clear indication of SFST analyses found that officers estimates of whether a motorist s BAC wasabove or below or percent were extremely accurate.

10 Estimates at the were accurate in 91 percent of the cases, or as high as 94 percent if explanationsfor some of the false positives are accepted. Officers estimates of whether amotorist s BAC was above but under were accurate in 94 percent of thedecisions to arrest and in 80 percent of the relevant cases, ReportValidation of the SFST battery at BACs Below Percent-- vi --Finally, the officers and prosecutors who were interviewed about the SFST sfound the test battery to be fully acceptable for FIELD use to establish probable causefor DWI results of this study provide clear evidence of the validity of theStandardized FIELD SOBRIETY Test battery to discriminate above or below percentBAC, using a slightly modified scoring procedure.