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Types of Field Sobriety Tests in California

Posted By The Law Office of Nors Davidson || 16-May-2013

If a law enforcement officer suspects that you are driving under the influence, they may administer a field sobriety test on the scene. Unlike a chemical test, which measures the amount of alcohol in a person's blood or on their breath, field sobriety testing is used to approximate the driver's level of intoxication. The National Highway Traffic Safety Administration's (NHTSA) standardized field sobriety testing involves three main tests:

Horizontal Gaze Nystagmus
Horizontal gaze nystagmus (HGN) involves the way in which the eyes naturally jerk when rotated at high peripheral angles. When intoxicated, nystagmus becomes more exaggerated even when the eyes rotate at lesser angles, and the eyes also have difficulty smoothly tracking moving objects. The officer will administer the HGN test by having you keep your head still and follow with only your eyes a small object such as a pen or flashlight as it moves horizontally in front of you. During the test the officer will look for such signs of impairment as:

  • You cannot track the object without moving your head
  • Your eyes jerk distinctly at maximum deviation
  • Your eyes jerk when the onset angle is within 45 degrees of the center
  • One or both of your eyes is unable to track the moving object smoothly

Walk and Turn Test
The walk and turn test assess your ability to divide your attention between tasks that are presumably easier for a sober person to perform. The officer will administer this test by having you take nine heel-to-toe steps along a straight line, turn on one foot, and then walk back to the start in the same way. The officer will observe you for signs of impairment, including:

  • You cannot balance while the officer gives instructions
  • You start to walk before the officer tells you to begin
  • You have to stop walking to regain your balance
  • You step off of the line
  • You must use your arms to balance
  • You take more steps than instructed

One Leg Stand Test
This test also evaluates your ability to perform two tasks at once that are assumed to be simple for a sober person. The officer will administer the test by instructing you to stand with one foot approximately six inches off the ground while counting out loud in thousands until you are told to stop. This test lasts for approximately thirty seconds, and during this time the officer will assess whether you exhibit any of the following indicators of impairment:

  • You swayed while standing on one foot
  • You had to hop to stay balanced
  • You had to put your arms out to balance
  • You couldn't count
  • You put your foot back on the ground before being told to do so

If you were charged with DUI after failing a field sobriety test, it is important to discuss your rights and the circumstances that led to your arrest with an experienced attorney. Our knowledgeable San Francisco DUI lawyer at The Law Office of Nors Davidson has successfully helped countless clients fight their drunk driving charges across the Bay Area, and can advocate for you as well. Contact our firm today to learn about your defense options!