After pulling a driver over on suspicion of DWI, the arresting officer will ask the driver to get out of the vehicle and perform a series of balance, coordination and vision tests. These tests, known as field sobriety tests, are designed to indicate whether an individual is intoxicated. In New York, three tests are generally given: the horizontal gaze nystagmus or HGN test, the one-leg stand and the walk-and-turn.

In order to administer the HGN test, the officer asks the driver to follow a moving object, such as a pen or a small flashlight, with their eyes as the officer moves it back and forth. If the driver’s eyes jerk or if the driver has difficulty following the object, it is considered a sign of intoxication.

The walk-and-turn and one-leg stand tests are intended to evaluate a driver’s balance and coordination. In the walk-and-turn test, the driver is asked to walk in a straight line for a given number of steps, heel-to-toe and then turn and walk back in the same manner. In the one-leg stand, the driver is asked to stand on one leg for 30 seconds. If the driver uses his or her arms to maintain balance, steps out of line during the walk-and-turn test or puts a foot down in the one-leg stand, it is viewed as evidence of intoxication.

The problem with all of these tests is that factors other than intoxication can significantly affect a person’s performance. These factors include age, physical health, any medical conditions and weight. These factors vary from one individual to another and the tests do not take these variations into account.

The potential consequences of a DWI conviction in New York are serious. They include license suspension, stiff fines and a possible jail sentence. An experienced DWI attorney can often challenge the reliability of field sobriety tests, which can result in a dismissal or reduction of the charges.

Source: National Highway Traffic Safety Administration, “Development of a Standardized Field Sobriety Test,” accessed Dec. 14, 2014