Field Sobriety Tests in Washington State

For decades, Washington State law enforcement agencies have administered certain physical tests to individuals suspected of intoxication. Nowadays, almost everyone who has consumed alcohol, or driven a car is aware of the Standard Field Sobriety Test’s, otherwise known as FST’s. Perhaps the most widely and best known test being, Walk and Turn, Heel-Toe test. The real question is though just how reliable are standard field sobriety tests?

In the mid-1970’s the National Highway Traffic Safety Administration (NHTSA), began a series of studies to develop standardized tests that could be administered by officers in the field to evaluate suspected intoxicated drivers. The studies resulted in the formulation of three recommended tests: (1) Horizontal gaze nystagmus (HGN), (2) Walk and Turn, Heel-Toe, and (3) One leg stand. A inability to perform the requested tests adequately has been considered sufficient to corroborate a officers conclusion that a person is intoxicated, based on objective signs. In the NHTSA standardized test battery, each of the three tests is administered and scored separately. Each test has a specific number of scoring points or “clues” that determine how the suspect should be classified. Observations made during all three contribute to whether an officer has probable cause for arrest.

FST’s were developed to provide statistically valid and reliable indications of a driver’s BAC, not indications of actual driving impairment. In the assigned studies, the researchers used BAC as the standard of measurement. That is, performance was correlated to BAC level only. There was no correlation made between performance and impairment, and no NHTSA study has ever evaluated the ability of the FST’s to accurately predict impairment.

In their findings the researchers noted that, certain diseases, neurological impairment and aging processes interfere with motor skills, and that officers may base assessments of intoxication on behavioral cues not derived from the tests. Moreover, some individuals exhibit a tolerance effect, where they perform in a manner that appears not to be congruent with their BAC level. Significantly, the studies ultimately concluded that it was easy to determine if a very impaired subject was above a .10% and that an alcohol free subject was below a .10%. However, the difficulty was and has continued to be in attempting to determine the borderline cases.

As a result, due to the many uncertainties and “confounding variables” involved, FST’s were never intended to be used to establish beyond a reasonable doubt, or that a persons actual BAC was in fact equal to or above the legal designation for DWI.

Remember, field sobriety tests are voluntary. If you have been arrested for DUI or are facing other similar charges, please contact Blair & Kim, PLLC today to see how a criminal defense attorney might be able to help you.


*Psychophysical Tests for DWI Arrest”, Final Report, Burns and Moskowitz, DOT HS-802 424, June 1977.

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