The Three Standard Field Sobriety Tests


When police are conducting an investigation to determine whether a driver is impaired or not, they will almost certainly request that the driver perform Standardized Field Sobriety Tests, which have been certified by the National Highway Traffic Safety Administration. There are three standard tests: Horizontal Gaze Nystagmus (HGN, the eye test), Walk and Turn, and One Leg Stand. You do not have to agree to take these tests; there is no consequence for refusing the tests.

HGN: Nystagmus refers to an involuntary jerking of the eyeball in response to a stimulus. When a person is under the influence of alcohol, this involuntary jerking can be more distinct. In this test, the subject is requested to follow a pen or a penlight (held about 12-15 inches away from the face) with his eyes only. The officer will then look for cues of nystagmus. It is important to note that a number of these cues may be naturally occurring in some individuals and may occur in others because of a head injury, stroke, inner ear disorder, or even vitamin deficiencies. Further, most laboratory testing uses a featureless background (a blank wall, for example), but the vast majority of HGN tests are administered along a busy roadside outdoors because of traffic stops. These kinds of backgrounds featuring movement and distractions are called “optokinetic backgrounds,” and these can impact how the eye tracks the stimulus and may even result in “false positive” clues.

Walk and Turn: In this test, the subject must stand on a line with his feet in the heel-to-toe position with her arms at her sides. She must then take steps down a line in a prescribed manner, turn around in a particular fashion, then take more steps until she has returned to her original position while counting her steps aloud.

One of the questions that arise because of this test is whether a person performing this test was a valid subject. Testing and research has found that people with injuries to their feet, legs, and back had difficulty performing the test even when completely sober. Persons over the age of 65 also had trouble with the test because of balance concerns. The lighting of the area where the test occurred is another concern; it’s much more difficult for someone to walk perfectly on a straight line when it’s extremely dark. Additionally, if the area is not level, the test will also be compromised.

One Leg Stand: In this test, the subject must stand with his heels together and arms at his sides. The subject must then stand on one foot and lift the other foot straight out and raise it approximately six inches off of the ground while counting aloud.

The Issues With Field Sobriety Tests


Like the Walk and Turn Test, people with feet, leg, or back injuries will likely have balance problems with this test, along with persons over the age of 65. This test will be much more challenging to execute if the area where a person must execute the test is uneven, filled with debris (like gravel), or if the person is not wearing appropriate shoes (for example, wearing high heels).

Although these tests have been certified by the National Highway Traffic Safety Administration, there are only certain persons who should be given the tests and only under certain circumstances, otherwise they lack scientific validity. In such circumstances, the guidelines have recommended that the tests should not be administered.

Both the Walk and Turn and One Leg Stand tests are “divided attention tests”; they are designed to examine whether an individual can focus on two different things at once. Can you listen to the instructions that the officer has given to you and remember how to properly execute it? Can you perform a physical exercise (walking, maintaining a particular pose, and balancing) and simultaneously perform a mental exercise (counting up to a particular number)? When impaired by alcohol, studies have shown that the greater one’s impairment, the more and more difficult it will be for a person to divide his or her attention. However, there can be other explanations for poor performance on a test that have nothing to do with alcohol impairment. An individual’s physical aspects play into this along with factor such as physical exhaustion, stress and anxiety, and Attention Deficit Disorder.

If the testing does not comply with the above referenced requirements, your attorney will be able to dispute whether the officer should have given you the tests at all and also whether your performance can be used as evidence during trial.