Field Sobriety Tests
Field or Roadside Sobriety Tests are used to establish probable cause for administration of a preliminary breath test, or for a drunk driving arrest and administration of a formal breath or blood test.
The Standardized Field Sobriety Test (SFST) is a battery of three tests administered and evaluated in a standardized manner to obtain validated indicators of impairment and establish probable cause for arrest. The tests administered under this protocol are the horizontal gaze nystagmus test, the walk-and-turn test, and the one-leg stand.
Divided Attention Testing - Tests which require a suspect to listen to and follow instructions while performing simple physical movements. Such tests include the walk-and-turn test and one-leg stand test.
Commonly administered sobriety tests include:
Counting - The suspect is asked to count forwards or backwards, usually by ones or threes. Signs of impairment include (1) skipping letters, (2) loss of concentration, and (3) slurred speech. This is not a particularly accurate or reliable sobriety test.
Finger to Nose - The suspect stands, usually with the head tilted back and eyes closed, with arms stretched out to his sides. The suspect then attempts to touch the tip of his index finger to his nose, first with one arm and then the other. Signs of imparment include (1) beginning before instructions are completed, (2) swaying or staggering, (3) using arms to balance, (4) losing balance, and (5) inability to touch fingertip to nose. This test can be difficult to perform even when sober, without practice.
Reciting the Alphabet - The suspect is asked to recite the alphabet, sometimes backwards. Signs of impairment include (1) skipping letters, (2) loss of concentration, and (3) slurred speech. This test is not particularly accurate, and may not be appropriate for suspects for whom English is not the primary language.
Standing on One Leg - The suspect is instructed to stand on one leg, with the other foot suspended approximately six inches off the ground and count aloud by thousands ("One thousand-one", "one thousand-two", etc.) until instructed to put the foot down. The officer times the suspect for thirty seconds. The officer looks for indicators of impairment, including (1) swaying while balancing, (2) using arms to balance, (3) hopping to maintain balance, (4) not counting in order, and (5) putting the foot down.
Walking a Line - A suspect is asked to walk a straight line. This should occur on a flat, even surface, at a safe distance from traffic. The officer looks for signs of impairment including (1) beginning before instructions are completed, (2) swaying or staggering, (3) using arms to balance, and (4) stopping walking to regain balance.
Walk-and-Turn - A suspect is instructed to take nine steps along a straigt line, walking heel-to-toe. After taking the steps, the suspect must turn on one foot and return in the same manner in the opposite direction. The examiner looks for seven indicators of impairment: (1) if the suspect cannot keep balance while listening to the instructions, (2) begins before the instructions are finished, (3) stops while walking to regain balance, (4) does not touch heel-to-toe, (5) uses arms to balance, (6) loses balance while turning, or (7) takes an incorrect number of steps.
Horizontal Gaze Nystagmus - Horizontal gaze nystagmus is an involuntary jerking of the eyeball which occurs naturally as the eyes gaze to the side. This test theorizes that when a person is impaired by alcohol, nystagmus is exaggerated, and that alcohol-impaired person will have difficulty smoothly tracking a moving object. To administer this test, an officer asks the suspect to watch a slowly moving object, such as a pen or small flashlight. As the officer moves the object horizontally (back and forth), the officer watches the suspect's eyes as they follow the object, watching for signs that (1) the eye cannot smoothly follow a moving object, (2) distinct jerking when the eye is at maximum deviation, and (c) an angle of onset of jerking within 45 degrees of center. The presence of four or more signs between a suspect's two eyes is considered to suggest unlawful intoxication. The circumstances of a roadside administration, or a lack of training for the officer administering the test, can significantly affect test results.