While police officers many times have drivers perform any number of “tests” on the side of the road to determine whether the driver is impaired or intoxicated, only three have been validated by the National Highway Traffic Safety Administration (NHTSA). They are the (1) Walk-and-Turn; (2) One-Leg-Stand; and (3) Horizontal Gaze Nystagmus tests. No other sobriety test (for example, the Alphabet Test, Finger Touch, Finger-to-Nose, Write the Alphabet, Pick up Coins, and others) is validated by the NHTSA. The NHTSA validated these three SFSTs after an extensive study commenced in 1977 by Anacapa Sciences of various Field Sobriety Tests being used by law enforcement throughout the country. As stated above, at the conclusion of the Anacapa study, the only three Field Sobriety Tests validated by the NHTSA were, and remain, the (1) Walk-and-Turn; (2) One-Leg-Stand; and (3) Horizontal Gaze Nystagmus.
It must also be noted that the SFSTs do not determine intoxication or “drunkenness”. In other words, they do not determine whether one is drunk. They are instead designed to determine whether one has a Blood Alcohol Concentration (BAC) above .10.
In order to accurately determine whether one’s BAC is above .10, SFSTs must be administered in accordance with national standards developed by the NHTSA. With regard to accuracy, studies have shown that if the three validated SFSTs tests are properly administered and the driver “fails” all three, there is an 80% chance that the driver has a BAC of .10 or greater. Therefore, even if the driver “fails” all three tests, there is still a 20% chance that his BAC is lower than .10. A 20% error rate surely raises reasonable doubt.
The Horizontal Gaze Nystagmus test is alone 77% accurate in determining a BAC of .10 or greater; the Walk-And-Turn alone is 68% accurate; and the One-Leg-Stand alone is 65% accurate. Accordingly, while the “failing” of these tests might be enough to establish probable cause to arrest, they certainly do not prove guilty beyond a reasonable doubt.
If you have been charged with Driving While Intoxicated (DWI) you need attorneys who are just as knowledgeable in the Standardized Field Sobriety Tests as the officer who arrested you. Tilem & Campbell managing partner, Peter Tilem, is certified in, among other things, Driving Under the Influence Detection having successfully completed the same eight hour course that many law enforcement members take. This course concentrated on, among other things, the proper administration of the Walk-and-Turn; One-Leg-Stand; and Horizontal Gaze Nystagmus tests.