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Standardized Field Sobriety Tests
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Burns, M. (2007). The robustness of the horizontal gaze nystagmus test (Report No. DOT DTNH22-98-D-55079). Washington, DC: US National Highway Traffic Safety Administration.
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.
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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 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.
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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 test at 0.08% BAC. The observational threshold of HGN, however, has not been estab lished. 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% - 0.12%. 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.
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Stuster, J., & Burns, M. M. (1998, August). Validation of the standardized field sobriety test battery at BACs below 0.10 percent. (Report no. DOT HS 808-839).Washington, DC: US National Highway Traffic Safety Administration.
This study evaluated the accuracy of the Standardized Field Sobriety Test (SFST) Battery to assist officers in making arrest decisions for 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 Standardized Field Sobriety Test 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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Burns, M. and Dioquino, T. (1998). Florida Validation Study of the Standardized Field Sobriety Test (SFST) Battery. Final Report to IPTM and State of Florida Department of Transportation.
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Burns, M. M., & Anderson, E. W. (1995, November). A Colorado validation study of the standardized field sobriety test (SFST) battery. Aspen, CO: Colorado State Department of Transportation.
In the State of Colorado, motor vehicle operators are subject to arrest if they are found to be driving with a blood alcohol concentration (BAC) over 0.05%. At BACs above 0.05% but less than 0.10%, they are charged with Driving While Ability Impaired (DWAI). At BACs of 0.10% and higher, the charge is Driving Under the Influence (DUI). These statutes reflect the evidence from both epidemiological and laboratory studies of alcohol impairment of driving skills. It is the responsibility of law enforcement officers to detect and arrest alcohol-influenced drivers in accordance with these statutory limits. In an effort to meet that objective, police officers, not only in Colorado but in all fifty of the United States, rely on a battery of standardized field sobriety tests (SFSTs). Observations of drivers’ performance of the tests, together with driving pattern, appearance and manner, odor of alcohol, and other signs, underlie officers’ arrest and release decisions. To be genuinely useful, roadside tests must be valid and reliable; i.e., they must measure changes in performance associated with alcohol and they must do it consistently. To the extent that they meet the validity and reliability criteria, they can be expected to contribute to traffic safety by increasing the likelihood that alcohol-impaired drivers will be removed from the roadway by arrest. Importantly, they also will further serve the driving public’s interests by decreasing the likelihood that a driver who is not alcohol-impaired will be mistakenly detained or arrested. Thus, the validity and reliability of the tests are important issues. This study was undertaken specifically to extend study of the SFSTs from the laboratory setting to field use. The primary study question was, “How accurate are officers’ arrest and release decisions when the SFSTs are used by trained and experienced officers?” Over a five-month period, officers from seven Colorado law enforcement agencies who volunteered for the study provided the records (N=305) from every administration of the SFSTs. Using only the standardized 3-test battery (Walk-and-Turn, One-Leg Stand, Horizontal Gaze Nystagmus), officers seldom erred when they decided to arrest a driver. Officers were more likely to err on the side of releasing drivers than on the side of incorrectly arresting drivers. Given the difficulty of the task which confronts officers at roadside, in particular with alcohol-tolerant individuals, the finding that approximately one-third of the released drivers should have been arrested is not unexpected. However, it is important to note that officers’ decisions to release were correct two-thirds of the time.It is concluded that the SFSTs are valid tests; i.e., they serve as indices of the presence of alcohol at impairing levels. The study design did not support an examination of test-retest reliability. It should be noted, however, that the test battery appears to have served equally well across agencies and officers, strongly suggesting that it achieves acceptable reliability as well.
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Tharp, V., Burns, M., and Moskowitz, H. (1981). Development and Field Test of Psychophysical Tests for DWI Arrest. U.S. Department of Transportation, National Highway Traffic Safety Administration, DOT-HS-805-864, Washington, D.C.
Administration and scoring procedures were standardized for a sobriety test battery consisting of the walk-and-turn test, the one leg stand test, and horizontal gaze nystagmus. The effectiveness of the standardized battery was then evaluated in the laboratory and, to a limited extent, in the field. Ten police officers administered the tests in the laboratory to 297 drinking volunteers with blood alcohol concentrations (BACs) ranging from 0 to 0.18%. The officers were able to classify 81% of these volunteers, on the basis of their test scores, with respect to whether their BACs were above or below 0.10%. Officer estimates of the BACs of people they tested differed by 0.03% on the average from the actual BAC. Interrater and test-retest reliabilities for the test battery ranged from 0.60 to 0.80. In a limited field evaluation police officers filled out 3128 data forms, each represented a driver stopped during a three month period. Police officers, after training on the administration and scoring procedures for the test battery, tended to increase their arrest rates and appeared to be more effective in estimating BACs of stopped drivers than they were before training. Anonymous breath testing of released drivers who were stopped indicated that many of the drinking drivers were never given a sobriety test.
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