An Analysis of Field Sobriety Test Accuracy

To better understand DUI charges and what can be done to challenge these, it is helpful to take an in-depth look at the accuracy of field sobriety tests and their influence on DUI cases. The following is an analysis of the standardized field sobriety test (SFST), a series of three tests most often administered in California DUI cases. (If a driver is disabled and unable to perform one or more of the standardized tests, different tests may be administered to accommodate this disability. If a driver is suspected to be under the influence of drugs, specialized field sobriety tests may be administered.)

The standardized field sobriety test includes three individual tests: the horizontal gaze nystagmus, the walk-and-turn and the one-leg stand. An analysis of each of these tests follows:

Horizontal Gaze Nystagmus

Typically considered the most accurate of field sobriety tests, the horizontal gaze nystagmus involves having a driver follow an object or light with his or her eyes. The officer will look for a side-to-side movement in the eyes as they follow the object or light, which is thought to indicate intoxication.

According to the National Highway Traffic Safety Administration, a 1998 study by Stuster and Burns revealed an accuracy rate of approximately 88%.


The walk-and-turn is a divided attention test that analyzes a driver's ability to listen to and carry out instructions involving physical movement. The driver is asked to walk nine steps, heel-to-toe, in a straight line. The driver must then turn on one foot and walk back in the same manner. The officer will look for trouble with balance, the wrong number of steps taken, the failure to touch heel to toe and starting before the directions have been completely given.

The same 1998 Stuster and Burns study revealed the walk-and-turn test was accurate 79% of the time.

One-Leg Stand

The one leg stand is another divided attention test. The driver is asked to stand on one foot with the other foot about six inches from the ground, while counting aloud. The officer will time the driver for 30 seconds and will look for balance issues, swaying, hopping or putting the foot down.

The 1998 Stuster and Burns study showed this test was accurate 83% of the time.

Accuracy Rates and What This Means in Your Case

Accuracy rates of 88%, 70% and 83% may seem high, but it is important to remember that these study results came from tests that were administered in accordance with NHTSA standards for field sobriety testing. What if a test is administered improperly? What if a factor having nothing to do with alcohol consumption affects a driver's results? Most importantly, what about the 12%, 30% and 17% of the times that these tests were not accurate?

It has been 16 years since the Stuster and Burns study, and yet these were the most recent accuracy results we could find on the NHTSA website. Even if they still hold true, there are many scenarios in which the accuracy of field sobriety tests can be brought into question by a skilled DUI lawyer. For example:

  • Was the test administered properly and completely in accordance with NHTSA guidelines?
  • Was the arresting officer experienced in administering field sobriety tests?
  • Were the tests conducted in a distracting or dangerous environment?
  • Was the driver wearing high-heeled shoes at the time of the walk-and-turn or one-leg stand?
  • Was the ground uneven where the walk-and-turn or one-leg stand were performed?
  • Did the driver have a medical condition that would cause a poor result on the horizontal gaze nystagmus test?
  • Was the driver unable to understand the officer's instructions due to a language barrier or disability?

These are just a few examples of defenses that may be brought up against "failed" field sobriety tests in a DUI case. The strategy and approach that work in your case will vary depending on the unique circumstances surrounding your arrest and testing. To learn more, involve an Orange County DUI lawyer from the Law Offices of Virginia L. Landry. We are experienced, dedicated and ready to fight for our clients' rights.

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