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Are field sobriety tests reliable?

On Behalf of | Sep 28, 2022 | DUI

Police officers conduct traffic stops when they think drivers are too impaired to drive. They have many tools at their disposal to determine what’s going on once they make contact with the driver. One of these is the field sobriety test.

The field sobriety test isn’t one single test. Instead, it’s a battery of tests the officer uses. When it comes to these tests, there are only some that are considered reliable. Tests that are commonly seen on television shows, such as saying the alphabet backward, aren’t part of that battery. These three tests that are reliable are part of the standardized field sobriety test.

What tests are part of the SFST?

There are only three tests that are endorsed by the National Highway Traffic and Safety Administration. These include:

  • Horizontal gaze nystagmus: This test looks at the eye movement when the driver is looking at an object held by the police officer. Alcohol impairment causes a jerking motion of the eyes.
  • One-leg stand: The driver has to walk heel-to-toe in a straight line then turn around and return to the starting point. Most people who are sober can do this without trouble, but impaired individuals will struggle.
  • Walk-and-turn: The driver has to stand with one foot six inches off the ground for approximately 30 seconds. It’s said that using the arm to balance, putting their foot down or swaying could point to an impaired driver.

While they’re considered reliable, these tests are also highly subjective. A big part of the problem is that the officer’s interpretation plays a role in the outcome of the test. When you consider all three tests combined, there’s an accuracy rate of around 91% for the SFST. That means that around 9% of people who go through the SFST are either accused of drunk driving when they’re sober or let go when they were impaired.

Officers typically use the SFST to determine if a driver should take a chemical test. Roadside tests aren’t considered reliable because of calibration issues. Because of this, drivers will usually need to go to the police department for a stationary breath test or to a medical facility to get a blood or urine test.

Fighting a drunk driving charge requires you to prepare a defense strategy. Part of this may be based on improper procedures being followed during the traffic stop. Working with someone who’s familiar with these cases is beneficial.