Field Sobriety Test

Many of us have seen television shows where someone has been pulled over by police and asked if he/she has been drinking, and then is asked to do all kinds of stunts to indicate whether he/she is intoxicated. Some are asked to say the alphabet, touch finger-to-nose, pick up coins, and so on. However, the United States Department of Transportation’s National Highway Traffic Safety Administration (NHTSA) only recognizes and recommends three tests to be used in the field by police officers investigating a drunk driving case.

These tests are: (a) the Walk-and-Turn test (WAT); (b) the One-Leg-Stand test (OLS); and, (c)the Horizontal Gaze Nystagmus test (HGN). Collectively, they are known as the Standard Field Sobriety Tests (SFST).
Walk-and-Turn Test
WAT is the well-known "walk the line" test. It requires the subject keep his/her arms at his/her sides look down at his/her feet, walk heel-to-toe down a straight line, turn by keeping the front foot on the line, use small steps to turn around completely, and then walk back down the line heel-to-toe. The police officer will require that the subject count his/her steps as well. The standard distance is nine steps.
To identify intoxication, the observing police officer will determine whether the subject: (a) kept his/her balance; (b) starts the test before the instructions are finished; (c) stops walking to steady him/herself; (d) does not touch heel to toe; (e) steps not just partially but completely off the line; (f) uses his/her arms for balance; (g) does not turn properly; (g) takes an incorrect number of steps.
If the subject fails two or more criteria, or fails to complete the test in its entirety, the police officer will identify the subject’s blood alcohol concentration (BAC) at .10% or above.

One-Leg-Stand Test
OLS is another well known test. It requires that the subject stand upright, keep his/her hands at his/her side, and while looking at his/her foot, lift it approximately six inches off of the ground and hold the position for thirty seconds. The police officer may require that the subject count out the thirty seconds. The police officer must remain motionless and stand at least three feet away from the subject.
To identify intoxication, the observing police officer will determine whether the subject: (a) sways while balancing; (b) uses his/her arms for balance or moves his/her arms more than six inches from his/her side; (c) starts hopping; (d) puts his/her foot down.
If the subject puts his/her foot down three or more times, it is construed as a total failure of the test. If the subject fails two or more criteria, or fails to complete the test in its entirety, the police officer will identify the individual’s BAC at .10% or above.
Horizontal Gaze Nystagmus Test

HGN is sometimes known as the "flashlight test." Initially the administrator of the test will require the subject to remove his/her eyeglasses. Next, the subject is questioned to determine if he/she has any naturally occurring conditions that can cause nystagmus, which is an involuntary jerking motion of the eyes. Thereafter, the administrator (i.e. investigating police officer), will hold an object, such as a pen or flashlight, vertically between 12 and 16 inches from the face, just above the level of the eye. The subject is instructed to keep his/her head still and to follow the object or stimulus only with his/her eyes. The administrator will then move the object slowly to each side of the head, ending at about the subject’s shoulder or ear and hold it there for four seconds. The test must be conducted in a well-lighted area, and the subject should be facing away from any flashing lights, traffic, or the police car.
While performing the test, the administrator will observe whether the subject has difficulty following the object, whether the eye is playing catch-up with the object, or whether the subject’s eyes are displaying the involuntary jerking motion called nystagmus. The more intoxicated a subject is, the sooner his/her eyes will start to "jerk" or oscillate.

One point will be assigned to each sign of intoxication per eye. The maximum score is six. A subject who received a score of four or more is classified with a BAC (blood alcohol concentrate) of .10% or above.
For a more in-depth discussion of HGN, please visit other parts of our website.