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FIELD SOBRIETY TESTING

المؤلف:  Max M. Houck، Jay A. Siegel

المصدر:  Fundamentals of Forensic Science

الجزء والصفحة:  376

2026-08-15

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FIELD SOBRIETY TESTING

When a driver is stopped by a police officer for driving under the influence of alcohol (DUIL), the subject is requested to perform some simple tests that might indicate his or her fitness to operate a motor vehicle. At one time, these tests were a necessary component of proof of OUIL or operating while impaired. Although these tests are no longer required as a component of proof in most states, they may still have an important function. In some states, specially trained police officers, called drug recognition experts can administer a battery of field sobriety tests to a driver. These tests, taken as a whole, can provide strong evidence that the driver is impaired or OUIL. They can provide probable cause to require further, quantitative alcohol testing. First developed in California, this battery of tests has spread widely across the United States. A typical protocol calls for three tests. The first is the horizontal gaze nystagmus. In this test, the subject is asked to follow with his or her eyes only, a pencil or other object as the officer moves it slowly back and forth across the subject’s field of vision. If a person is sober, he will be able to follow the pencil easily and his eyes will move smoothly. If, however, the person is under the influence of alcohol (or certain drugs), the eyeballs will jerk as they move. The other two tests measure dexterity, which would be expected to deteriorate as BAC increases. Common ones are the “walk and turn” whereby a person must walk in a straight line putting one foot directly in front of the other and then turn around and come back. The other test is to close one’s eyes and touch one’s nose with the tip of a finger. When all three tests are used as a set, there is a high correlation between drunk or drugged behavior and the results of these tests.