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DWI Detection and Standardized Field Sobriety Testing : Empowering Law Enforcement

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DWI Detection and Standardized Field Sobriety Testing : Empowering Law Enforcement HV 8079 .076 093 ~- · DWI Detection 2001 0 Standardized Field Sobriety Testing \ ••••••••••••••••••••••••••••••••••••••••••••••••••• • • • • •••••••••••••••••••••••••••••••••••••••••••••••••••• • Bureau of Transportation Safety (~)f{b~ in cooperation with ¾,,"""''''''~$§ HS115 2/01 University of Wisconsin Resource Center on Impaired Drivinq r' DWI Detection and Standardized Field Sobriety Testing Empowering Law Enforcement DWI Detection and Standardized Field Sobriety Testing INTRODUCTION Since the advent of the automobile in the late 19th century, driving while intoxicated (DWI) 1 has been a problem and a significant challenge for law enforcement officers. The family car has become an American institution; ownership is within the means of virtually every citizen. We value our freedom and independence and view driving as a basic right, not a privilege. This perception, combined with a societal attitude that accepts the premise that one can drink and still drive safely as long as one does not become "drunk," challenges law enforcement officers to sort out the drivers who have had only "two beers," from those who are legally "drunk" and thus a menace to society. In an effort to assess a driver's level of impairment, law enforcement officers traditionally employed a wide variety of simple tests of balance and coordination skills. Over time, observation of persons under the influence led to the development of relatively simple tests; such as, walking heel-to-toe in a straight line, touching the tip of the fing-er to the nose, picking up coins, etc. These tests were commonly accepted in court as evidence ofimpairment, especially when presentedwith other corroborating facts. In the early stages of DWI enforcement, most states had a higher statutory limit than what is currently permissible. At a higher legal limit, it was easier to convince juries and judges that arrested drivers were legally "drunk" based on an officer's commonsense observations. However, as we learned more about the effects of alcohol and other drugs on a person's ability to safely drive an automobile, the accuracy of the traditional tests began to be questioned. There was a large disparity both in the number and the types of field sobriety tests administered by law enforcement officers across the country. Another significant problem was that the tests were not administered or interpreted in any standard way, and persons not under the influence of alcohol were just as likely to "fail" the tests as those who were impaired. Basically each officer had the discretion to administer and interpret as many and as varied tests as he or she chose. 1. DWI is used here in a generic sense to refer to impaired driving. Similar designations for the offense include OWI, OMVWI, and DUI. 1 RESEARCH AND DEVELOPMENT OF STANDARDIZED FIELD SOBRIETY TESTS (SFSTs) Phase I. In 1976, the National Highway Traffic Safety Administration (NHTSA) funded a comprehensive research program to: (1) evaluate currently used physical coordination tests to determine their relationship to intoxication and driving impairment; (2) develop more sensitive tests that would provide more reliable evidence of impairment; and (3) standardize the tests and observations. Studies measuring performance of complex skills in driving indicated that any alcohol, even at the lowest measurable levels, produces some impairment. In the analysis of driving tasks, researchers focused mainly on how alcohol affects those tasks requiring divided attention (concentrating on or performing two or more tasks at the same time). Many of the most reliable and useful roadside tests employ the concept of divided attention. Driving is a complex task, composed of many components, both mental and physical tasks. Alcohol and other drugs reduce a person's ability to divide his or her attention. Drivers under the influence of intoxicants must often ignore less critical components of driving and focus their impaired attention on the mote critical tasks. A driver might focus on steering and speed control and ignore signaling or processing information from traffic control signals or signs. Even while impaired, some people often handle a single focused-attention task fairly well. A driver might be able to keep a car within a proper traffic lane, as long as the road remains fairly straight. However, most people who are under the influence cannot satisfactorily divide their attention to handle multiple tasks at once. The best tests of impairment call for the same mental and physical capabilities that you need to drive safely. Any test that simultaneously calls for a person to demonstrate two or more of these capabilities is a good potential candidate for a roadside test. Researchers analyzed a wide array of commonly used sobriety tests and narrowed potential tests down to the following six: • one-leg stand • finger to nose 2 • finger count • walk and turn • tracing (a paper and pencil test) • nystagmus (an involuntary jerking of the eyes) Researchers analyzed their data and found the presence of specific, identifiable clues from all six tests that could be used to correctly classify a volunteer's alcohol concentration (AC)2 as being either above or below 0.10% about 83 percent of the time. Further, the researchers found that this same level of accuracy could be achieved by considering results of just three tests: nystagmus, walk and turn, and one-leg stand. This three-test battery clearly appeared to offer an objective and predictable field sobriety testin-g procedure. Phase II. In view of this success, NHTSA funded a second phase of research in 1980 to: (1) complete the development and validation of the sobriety test battery, and (2) assess in the field, the battery's feasibility and its effe~tiveness for estimating AC as well as facilitating identification of persons with ACs above 0.10%. Standardized procedures for conducting the tests were refined and subjected to further testing in the laboratory and in the field. Results of the laboratory study demonstrated that the three-test battery could be used to correctly and objectively distinguish subjects with ACs of 0.10% or more from those with lower ACs. NHTSA analysis of the test data found that the nystagmus test, by itself, could produce 77% accurate classifications. Similarly, walk and turn was capable of 68% unaided accuracy, and one-leg stand of 65%. NHTSA also found_that it was possible to combine the results of nystagmus and walk and turn in a "decision matrix" to achieve 80% accuracy. During the field study, the researchers found that after training on the test battery, officers tended to make more arrests. Further, trained officers were more accurate in identifying suspects with ACs above 0.10%. The overall conclusion of this study was that the test battery works well. However, it remained necessary to duplicate these laboratory tests in the field. Phase III. The third phase of the research was a large scale field validation. The objectives were to: 2 This is also commonly referred to as "blood alcohol concentration" or BAC. 3 (1) develop standardized, practical, and effective procedures for officers to use m reaching a decision to arrest or not to arrest; (2) test the feasibility of the procedures in operational conditions; and (3) secure data to determine if the tests would work as well in the field as in the laboratory. The research staff began by re-analyzing the data with a view toward systematizing the administrative and interpretive procedures for the three tests. The intent was to ensure that the tests would be quick and e_asy to use, that they could be used independently of one another; i.e., if the officer is limited to only one or two of the tests due to unusual circumstances, and that they would maximize the detection of drivers at A Cs of 0.10% or more while minimizing the continued investigation of drivers below that level. Essentially, the current administration and interpretation procedures for the three tests emerged from this re-analysis. WHAT DID THE RESEARCHERS LEARN? The three tests - nystagmus, walk and turn, one-leg stand - were found to provide specific and predictable indicators for identifying subjects with ACs of 0.10% or more. Considered individually, the nystagmus test (now commonly referred to as horizontal gaze nystagmus or HGN) was the most accurate ofthe three: among subjects who exhibited four or more clues, 82% had ACs of 0.10% or higher. The other two tests were nearly as accurate, 80% for walk and turn, and 78% for one-leg stand. When nystagmus and walk and turn results were jointly interpreted using the decision table, they proved capable of correctly classifying 83% ofthe subjects. The importance of this large scale validation study deserves to be emphasized. It was the first significant assessment ofthe "workability" ofthe standardized tests under actual enforcement conditions, and it was the first time that completely objective clues and interpretation criteria had been defined for the tests. The results of the study unmistakably validated the standardized field sobriety tests. Why should I have my officers learn this technique when they have successfully been arresting drunk drivers for years? The chief advantage in using this test battery is that it is supported by scientific research and proven validation techniques. An officer will be able to go into a hearing or a courtroom and testify about specific and predictable clues ofimpairment with scientific objectivity previously unavailable to officers at roadside. Also, using SFST does not preclude an officerfrom using other roadside tests, such as reciting the alphabet or finger count. In today's society it is estimated that 2,000 alcohol-impaired trips occurfor every 4 arrest, it is very important that officers do not miss signs of impairment especially in individuals with high alcohol tolerance levels. FIELD RESEARCH THE CALIFORNIA STUDY The purpose of this study was to evaluate the accuracy of the SFST battery in assisting officers to make arrest decisions for DWI at alcohol concentration levels below .10 percent.
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