One Leg Stand Test

For decades, police officers have used voluntary tests to determine possible intoxication of drivers. The tests varied: a driver might be asked to touch a finger to the nose, stand on one leg, or walk a straight line. No studies were available to determine the tests’ fairness.

In 1982 the National Highway Traffic and Safety Administration (NHTSA) finalized three tests that fairly reliably determine a driver’s intoxication level.

These tests are to give an officer ‘probable cause’ to arrest the driver on suspicion of DUI. The officers are trained by the NHTSA to administer these tests in a manner that provides consistent results.

So as not to provide a defense attorney with reasons to have the results dismissed, the test is given in adequate lighting on level, dry ground. If these conditions cannot be met, the officer attempts to move to a better area or uses the results of the horizontal gaze nystagmus (HGN) test alone, as the walk-and-turn test requires the same optimal conditions as the one-leg stand test. Officers are aware that the elderly and overweight often have difficulty with such requests when sober and take that into account.

The driver stands with the heels together and arms at the sides. When instructed, the driver raises one foot about six inches and at the same time counts quickly from 1001 to 1030. The driver looks down at the raised foot while counting.

In the above tests, the officer is looking for loss of balance indicators, watching for swaying, overusing the arms for balance, hopping, or an inability to keep the foot raised. The officer tallies one point for each mistake, counting to five points as a failure indicator.

The test has a 65 percent reliability that a driver is impaired (BAC of .10 percent or higher) if the driver cannot perform this action. Combined with the walk-and-turn test, reliability is about 80 percent. While a driver may politely refuse to take standardized field sobriety tests, this in itself is an indication of possible guilt and permits the officer to arrest the driver for probable cause. In most states the driver’s license is immediately suspended or revoked for refusing to take this test. Repercussions can be more severe for refusing to take the test than if the driver took the test and failed.