Standardized Field Sobriety Tests (SFST's)
Law enforcement officers have utilized field sobriety tests to determine the impairment of a persons driving due to alcohol influence since shortly after automobiles appeared on the public roadways. Prior to Breath Alcohol Testing, the officer's opinion of a driver's performance on field sobriety tests was usually the only measure of impairment.
The performance of the field sobriety tests was used by the officer to make the all important decision whether probable cause existed for making a DUI arrest and depriving a person of their freedom.
Additionally, performance on field sobriety tests was often the only evidence introduced against a person suspected of driving under the influence in the post arrest DUI court proceedings.Beginning in 1975, a movement arose to assign scientific legitimacy to field sobriety testing by developing Standardized Field Sobriety Tests (SFTS's). Accordingly, in late 1975, extensive research studies were sponsored by the United State's Department of Transportation's (DOT) National Highway Traffic Safety Administration (NHTSA). These studies were sponsored through a contract with the Southern California Research Institute (SCRI) to determine which of the roadside field sobriety tests which had evolved were most accurate.
Three reports were published by SCRI. In 1977, a study was published based upon a research conducted in California. Thereafter, in 1981, a study was published based upon further research conducted in California. Finally, in 1983, a study was published based uopon research conducted in Maryland, Washington, D.C, Virginia and North Carolina. During this entire period, SCRI traveled throughout the United States in order to select the most commonly used field sobriety tests.
Ultimately, six tests were selected for review in the initial stages of the study. The SCRI researchers concluded that three of the six tests were accurate for distinguishing individuals having a Blood Alcohol Concentration (BAC) or Blood Alcohol Level (BAL) of 0.10%. One of the three tests, Horizontal Gaze Nystagmus (HGN), is actually an eye examination. The remaining two tests selected were the One Leg Stand (OLS) and Walk and Turn (WAT), primarily rely upon balance, coordination and the ability to follow the directions of the officer administering the Standardized Field Sobriety Tests.
The National Highway Traffic Safety Administration (NHTSA) concluded Horizontal Gaze Nystagmus was 77% accurate. The One Leg Stand was 65% accurate. The Walk and Turn was 68% accurate. However, when interpreted together, interpretation was represented to lead to a higher degree of accuracy.
Non Standardized Field Sobriety Tests continue to be used by law enforcement agencies, including the San Francisco Police Department and the California Highway Patrol. These can include the Rhomberg Balance, Finger Tap, Hand Pat, Written Alphabet, and Finger to Nose Field Sobriety Tests.