Types Of Field Sobriety Tests

To be clear, you should never perform any field sobriety tests. You should decline an invitation to perform field sobriety tests (as it is simply a request), so it is not necessary for you to be familiar with them or to know what the officers are looking for in determining if you are impaired. In fact, many sober adults may perform in a manner that an officer could interpret as indicating impairment for a variety of environmental or physiological reasons.

1. The walk and turn test

For instance, one common field sobriety test that law-enforcement officers employ is called the “walk and turn” test. A driver is asked to exit a vehicle and walk, heel-to-toe, along a straight line. One is asked to stop after a number of paces (typically 9), turn around by planting one foot and making a series of smaller steps in a circle, and return, walking heel-to-toe along the straight line (whether an imaginary line or an actual line). Depending upon a their physical characteristics, age, weight, physical fitness and relative balance, many sober adults may fail this test by falling off the line, failing to turn correctly, failing to walk heel-to-toe, or failing to follow directions properly. The tests are very subjective. Therefore it is up to the already suspicious officer to determine if there are any signs of impairment to warrant your arrest. Some people operate under the impression that they can handle the test. However, even things like beginning the test too early can be considered a clue to your impairment. The bottom line is, do not do the test!

2. The one-leg stand test

Another common test that law-enforcement officers employ in DWI investigations is the so-called “one-leg stand.” During this test, a person is asked to balance upon one leg for a period of time—usually up to thirty seconds. They will ask you to select one leg and life your leg six to eight inches off of the ground with a pointed toe while keeping your arms down at your side and remaining balanced with no wobbling and keeping your toe off the ground. Again, depending upon their physical characteristics and condition, even sober adults may have difficulties performing this test. It is likely, if you agree to perform the test, that a law-enforcement officer will be able to single out one or more features of the test that, in the officer’s view, point to your impairment.

3. Nystagmus tests

Officers also commonly employ so-called nystagmus tests during field-sobriety testing. Nystagmus is defined by the National Highway Transportation and Safety Administration as an involuntary jerking or bouncing of the eyeball that occurs after the ingestion of central nervous system depressants including alcohol.

The most common type of nystagmus test that law-enforcement officers employ is the “Horizontal Gaze Nystagmus.” Horizontal gaze nystagmus refers to lateral or horizontal jerking of the eyes when they gaze to the side. When administering this test, officers look for a total of six clues—three in each eye. The first clue is “lack of smooth pursuit.” An officer moves an object slowly but steadily from the center of a person’s face towards one’s left ear. The person’s left eye should smoothly follow the object. If the eye bounces or jerks, this “clue” is recorded. The “lack of smooth pursuit” test is repeated for the person’s right eye.

Next, an officer will look for “distinct nystagmus at maximum deviation” by starting again at the center of a person’s face and moving the object over to one’s left ear. The officer will direct a person to follow the object with one’s left eye as far as possible, and then hold the object steadily for four to five seconds. Holding one’s gaze upon the object will ensure that bouncing or jerking of the eye was not caused by an officer moving the object too quickly. If distinct, sustained bouncing or jerking is observed, the clue is recorded. This process is repeated for the right eye.

The third and final horizontal gaze nystagmus test involves the “angle of onset of nystagmus prior to forty-five degrees.” During this test, an officer moves the object at a speed that should take around four seconds for the object to reach the person’s left shoulder. If the point or angle at which the left eye begins to display nystagmus occurs before the officer reaches forty-five degrees from the center of the person’s face, the clue is recorded. The process is repeated for the right eye.

Amazingly, the National Highway Transportation Safety Administration recommends, for safety reasons, that officers “use no apparatus to estimate the forty-five degree angle.” This underlines the very subjective nature of nystagmus tests and of field-sobriety tests in general. Who, other than the law-enforcement officer, is present to verify that a person’s eyeball is bouncing or jerking? Dashboard video cameras—if they capture field sobriety tests at all—are not equipped to focus upon a person’s face to a point at which nystagmus may be verified.

In the end, a person’s performance on field-sobriety tests will be largely in the eye of a beholder, and that beholder—more often than not—is going to be the law-enforcement officer who suspected you were driving while impaired in the first place.

Continue reading: Field Sobriety Tests - What Are My Rights?