Driving Under the Influence Field Sobriety Tests

Horizontal Gaze Nystagmus

Nystagmus is the unconscious movements of the eye. Generally, this movement is considered as the sign of alcohol consumption. Presence of an intoxicant in the body has nothing to do with nystagmus. Few elements make nystagmus without affecting the driving ability of a person. Nystagmus occurs in person by birth due to heredity or can be a result of structural neurological ailment.

Some of the signs of alcohol impairment arising while testing nystagmus is failure to keep the head unmoving and making of incriminating statements; however, these actions do not cause the deduction of points in test.

There are several conditions that may affect the performance of the suspect while nystagmus test. These conditions include eye irritation caused by wind, dust and rain, having a synthetic eye, optical disruption that obstruct the test like blinking lights, traffic and rain and having injured or frail vision in one eye. People who are not affected with the influences may show evidence of nystagmus. Some pathological diseases like brain damage, ear problem or brain tumors can also cause the nystagmus.

Walk and Turn

The walk and turn method tests the posture of suspect. In this procedure, the person needs to sustain heel-to-toe posture unless the officer instructs him or her to walk. The person is then asked by the office to take nine heel-to-toe steps and return to the starting position while maintaining the same position of heel-to-toe. The turn is completed by taking small steps with the help of one foot while maintaining the front foot’s position. The person has to keep his or her hands at his side, make a close observation of their feet and count up each step loudly. In this test, the suspect’s performance can be affected by some conditions like the footwear of the person, highway traffic, age factor and bad weather conditions.

One Leg Stand

This test asks the person to stand with his or her feet together with both arms at their side until they receive instructions from the officer. Some instructions are given to the suspects like standing still on one leg, keeping the leg in forward position so that the raised foot is parallel to ground and holding out the foot six inches off the ground. The person may be asked by the officer to stand still around 30 seconds while tracking every second. In all the conditions, the suspect has to keep his or her arms at their side and observe the raised foot.

Some conditions my affect the person’s actions and performance like age of 60 years or above, excessive weight, footwear and any kind of medical problem or disease.

Non-Standardized Field Sobriety Tests

Some more non-standardized tests that are accepted by a few organizations in the U.S. (including the International Association of Chiefs of Policehttp://www.theiacp.org/ and the National Park Service) include the hand pat test, the alphabet test, finger to nose test, the finger count test, the reverse counting test and the coin pick up test.