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Field Sobriety Tests

Field Sobriety Tests (FSTs) are very commonly encountered on the road. Juries often seem to be impressed with their seemingly objective and scientific nature. However FST are lose-lose for the defendant. If they do poorly on these completely subjective tests, then they will be considered drunk and presented as such by the prosecutor. If they do well, often times the prosecution will say this is an indication of a high tolerance for alcohol and is essentially a backhanded accusation of alcohol abuse.

It is important to understand that FST are not reliable and in fact are not objective. In one study, 14 police officers were shown video tapes of multiple FSTs on various subjects and were asked to determine based on watching whether or not they are impaired. Nearly 50% of the time the officers indicated the driver unfit to drive. What they did not know, however, was that all of the subjects had a BAC of 0.0% and none had ingested any alcohol.

The purpose of a FST is to determine probable cause for arrest. There are 4 categories of FST: 3 of them are performance tests and one is an eye impairment test. Of the performance tests, 2 are physical tests and one is a mental test, however it is common that a mental and physical test be combined. The first category is a balance test. The most common FSTs are the One-leg stand and the walk-and-turn. The second physical test is coordination. Here the common tests are finger-to-nose and finger-to-thumb tests. The third performance test is mental agility. Most common are reverse counting and reciting the alphabet. Finally, the last type is eye impairment tests. Here the officer conducts tests such as pupil reaction and gaze nystagmus to determine the possibility of impairment.

Explaining SFST

As stated earlier, despite the wide variety of tests and their seemingly scientific nature, FSTs are wholly unreliable. In fact, the National Highway Traffic Safety Administration (NHTSA) conducted extensive experiments on all FSTs and concluded that most were in fact unreliable. NHSTA did recommend that a three-test battery, commonly referred to as the standardized field sobriety tests (SFST's) be used under specific guidelines and a standard objective scoring system. The three standard tests are the walk-and-turn, and one-leg stand, and the horizontal gaze nystagmus.

All of these have extensive guidelines on how they are to be conducted, what indicators indicate impairment, and instructions that need to be given to the subject at the start of the test. After their research NHTSA has stated that these three tests are the only tests rooted in some scientific value and are reliable indications of impairment. Even then, the study concluded that in laboratory conditions, these tests administered together were correct only 83% of the time.

There are a variety of other FSTs that are not considered standardized. These "alternative FSTs" are laid out in the California Highway Patrol (CHP) manual as only to be used when the standardized tests cannot be administered. Those tests are as follows: the Romberg balance test, finger-to-nose test, hand pat, finger count, and alphabet FST. However, these are still considered to be unreliable by the NHTSA.

Walk-and-Turn (WAT)
The walk and turn test is where the subject is required to walk in a straight line from one point to another. The NHTSA guidelines requires that it be conducted on a smooth, flat surface, the subject take nine steps heel-to-toe, the subject must count steps out loud, keep their arms at their sides, and be staring at their feet. They are also not allowed to stop until they have reached the end. There are eight indications of impairment for this test:

  1. Cannot keep balance
  2. Starts too soon
  3. Stops too soon
  4. Does not put heel to toe
  5. Steps off of the line
  6. Does not keep their arms to their sides
  7. Wrongly turns
  8. Takes the incorrect amount of steps

One-Leg Stand (OLS)
This test also requires a smooth flat surface. This tests consists of lifting one leg off the ground and holding it straight out in front of you in order to determine balance. The specific guidelines for this test are they must extend on leg stiff roughly 6 inches off the ground. The subject must also count out loud for 30 seconds. This test employs divided attention. There are 4 indications of impairment for this test:

  1. Swaying
  2. Using arms to balance
  3. Hopping
  4. Putting foot down

Horizontal Gaze Nystagmus (HGN)

Here the subject must follow a moving object using only their eyes. The officer must use a horizontally moving object to conduct the test. Nystagmus refers to the jerking of the eyes. Impaired individuals eyes jerk much sooner than a sober person. This test has 6 indications of impairment:

  1. Lack of smooth pursuit in left eye
  2. Lack of smooth pursuit in right eye
  3. Distinct nystagmus at maximum elevation in left eye
  4. Distinct nystagmus at maximum elevation in right eye
  5. Angle of onset prior to 45 degrees in left eye
  6. Angle of onset prior to 45 degrees in right eye

Lawyers at our firm have been certified by the International Association of Chiefs of Police (IACP) and the National Highway Transportation Safety Administration (NHTSA) to both administer and evaluate field tests, and are certified on the Alco-sensor Preliminary Alcohol Screening (PAS) device commonly used in DUI investigations. Our firm knows how to dispute test results and can provide strong legal representation in your DUI case.

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