PUBLICATIONS BY TOPIC: SFSTs

Burns, M. (2007). The robustness of the horizontal gaze nystagmus test.

Police officers follow procedures set forth in the NHTSA/IACP curriculum when they administer the Standardized Field Sobriety Tests (SFSTs) to suspected alcohol-impaired drivers. The SFSTs include Horizontal Gaze Nystagmus (HGN) test, Walk-and-Turn (WAT) test, and One-Leg Stand (OLS) test. Courts generally accept testimony about WAT and OLS, but may not admit testimony about HGN. It has been argued that variations from standard procedures in HGN administration affect its validity and should render testimony about it inadmissible. Three experiments examined the effects of procedural variations in administration of the HGN test. Variations in stimulus speed and elevation, and distance of the stimulus from the suspect’s face were examined in a laboratory experiment. A second experiment conducted in training workshops varied the participants’ positions (standing, sitting, lying down). The third experiment examined HGN in participants who have functional vision in only one eye. The data demonstrate the validity of the HGN test with both standard and varied testing procedures. The variations did not alter the occurrence of, or the observations of, HGN. 

Burns, M. (2003). An overview of field sobriety test research. Perceptual and Motor Skills, 97, 1187-1199. 

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 roadside 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.

Burns, M., Fiorentino, D. and Stuster, J. (2000). The Observational Threshold of Horizontal Gaze Nystagmus. Proceedings, 15th International Conference, Alcohol, Drugs and Traffic Safety, Stockholm, Sweden.

Laboratory studies of field sobriety tests, which were conducted during the 1970s, identified horizontal gaze nystagmus (HGN) as a sensitive and reliable marker of alcohol at BACs of 0.10% and above (Burns & Moskowitz, 1977; Tharp, Burns, Moskowitz, 1981). In a more recent study, McKnight, Langston, Lange, and McKnight (1995) found that HGN remains a valid field sobriety tests at 0.08% BAC. The observational threshold of HGN, however, has not been established. A study was undertaken to further examine HGN at 0.08% BAC and to determine the lowest BAC at which its signs appear reliably. Measurements of the angle of gaze (AOG) at the onset of nystagmus were obtained with 48 subjects, who had been given alcohol to produce peak BACs in the range 0.02% - .012%. Observations were made with the EM/1, an instrument which displays a magnified video image of subjects’ eyes. The obtained data provide further evidence of the reliability of HGN as an index of the presence of alcohol at 0.08%. Further study will be required to establish a BAC threshold for HGN.

Stuster, J., & Burns, M. M. (1998). Validation of the standardized field sobriety test battery at BACs below 0.10 percent.

This study evaluated the accuracy of the National Highway Traffic Safety Administration's (NHTSA's) Standardized Field Sobriety Test (SFST) battery to assist officers in making arrest decisions for Driving While Intoxicated (DWI) at blood alcohol concentrations (BACs) below 0.10 percent. NHTSA's SFST battery was validated at 0.10 percent BAC in 1981. The trend to reduce statutory DWI limits to 0.08 percent BAC prompted this research project. The research was composed of several project tasks, including planning, site selection, training, data entry, and data analysis, in addition to the actual conduct of a major field study. The City of San Diego, California, was selected as the site. Seven officers of the San Diego Police Department's alcohol enforcement unit were trained in the administration and modified scoring of NHTSA's SFST battery (i.e., Horizontal Gaze Nystagmus-HGN, Walk and Turn, and One Leg Stand). SFST scoring was adjusted: the observation of four HGN clues indicated a BAC >/= 0.08 percent (rather than four clues indicating a BAC >/= 0.10 percent), and the observation of two HGN clues indicated a BAC >/= 0.04 percent. During routine patrols, the participating officers followed study procedures in administering SFSTs and completing a data collection form for each test administered. The officers' final step in each case was the administration of an evidentiary breath alcohol test. Data analysis found the SFSTs to be extremely accurate in discriminating between BACs above and below 0.08 percent. The mean estimated and measured BACs of the 297 motorists tested were 0.117 and 0.122, respectively; the difference between the means (0.005 percent BAC) is very small and operationally irrelevant. Further, analyses found the HGN test to be the most predictive of the three components of the SFST battery (r=0.65), however a higher correlation was obtained when the results of all three tests were combined (r=0.69). Decision analyses found that officers' estimates of whether a motorist's BAC was above or below 0.08 or 0.04 percent were extremely accurate. Estimates at the 0.08 level were accurate in 91 percent of the cases, or as high as 94 percent if explanations for some of the false positives are accepted. Officers' estimates of whether a motorist's BAC was above 0.04 percent but lower than 0.08 percent were accurate in 94 percent of the decisions to arrest and in 80 percent of cases overall. Also, the officers and prosecutors who were interviewed about the SFSTs found the test battery to be acceptable for field use to establish probable cause for DWI arrest. The results of this study provide clear evidence of the validity of the SFST battery to discriminate at 0.08 percent BAC, using a slightly modified scoring procedure. Further, study results strongly suggest that the SFSTs also accurately discriminate at 0.04 percent BAC.

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