Standardization Vital to Field Test Reliability
The Importance of Standardization
The validity of SFST results is dependent upon practitioners following the established, standardized procedures for test administration and scoring. NHTSA’s SFST Student Manual states that the procedures demonstrated in the training program describe how SFSTs should be administered under ideal conditions, but that ideal conditions do not always exist in the field. Variations from ideal conditions, and deviations from the standardized procedures, might affect the evidentiary weight that should be given to test results.
Courts in several states have reviewed the admissibility of field sobriety tests that assess physical coordination and have held that deviations in the administration of the tests should not result in the suppression of test results. These courts have found that field sobriety tests, including the Walk-and-Turn and the One-Leg-Stand of the SFST battery, are simple physical dexterity exercises that can be interpreted by an officer in the field, and by others in a court of law. However, courts have ruled that the admissibility of the HGN test may be treated differently due to its “scientific nature.” For this reason, HGN results are vulnerable to challenge, and likely to be excluded by the court, if the test was not administered in strict compliance with established protocols.
Other states have been even less accommodating to deviations from the standardized procedures. In particular, the Ohio State Supreme Court ruled that law enforcement officers have no discretion in the administration of SFSTs. In a four-to-two decision, the Ohio State Supreme Court held in Ohio v. Homan, 732 N.E.2d 952 (Ohio 2000), that Standardized Field Sobriety Tests conducted in a manner that departs from the methods established by NHTSA “are inherently unreliable” and thus inadmissible.4
The SFST battery is composed of three separate tests with three independent predictive validities that range from 79 to 88 percent. Depending on the physical characteristics of the subject and roadside conditions, an officer might choose to refrain from administering the entire SFST battery, as directed by the training materials (e.g., a leg injury that might affect a person’s ability to perform the OLS test). Because an officer is permitted the discretion to withhold a test, it is reasonable to question why a deviation in the administration of one of the three tests would disqualify the entire battery. Although it is not recommended to do so under ideal conditions, the data show that accurate arrest decisions reliably can be made on the basis of two of the SFSTs, or on the basis of HGN test results, alone.
The International Association of Chiefs of Police (IACP) adopted uniform procedures in 1992 to guide the training of SFST instructors and practitioners. Those standards include 24-hours of NHTSA-approved SFST instruction. The procedures for administering and interpreting SFST results can be readily learned and, generally, proficiency increases with experience. However, it is possible for SFST skills to degrade if they are not exercised regularly (e.g., during a prolonged absence from patrol work). Also, the SFST procedures have evolved since they were first developed in 1981. Modifications to the standardized procedures could result in an officer administering SFSTs according to outdated protocols.5 For these reasons, NHTSA recommends that law enforcement agencies conduct refresher training for SFST instructors and practitioners.