How does a field sobriety test work?

How does a field sobriety test work?

Wisconsin is one of many states where police officers use field sobriety tests in effort to determine if a driver is under the influence of alcohol or drugs.

Oftentimes, filed sobriety tests are conducted in order for the officer to determine if there is “probable cause” to require the driver to submit to a breathalyzer test or a blood test.

A field sobriety test is conducted along the roadside and there are several variations that can be used, including:

  • Walk-and-turn: The motorist must walk heel-to-toe in a straight line for nine steps, then turn around and return.
  • One-leg stand: The motorist must stand with one foot raised about six inches off the ground while counting out loud.
  • Horizontal gaze nystagmus (HGN): The involuntary twitching of the eye is tested as the motorists looks from side to side.

According to federal standards that are followed by most police departments, field sobriety tests should only be conducted in certain conditions and under certain procedures. If these standards are not followed by police officers, it is possible that the DUI or OWI charge could be dismissed.

For example, one of the standards requires that a field sobriety test only be administered on dry, even pavement. If a motorist is pulled over on a snowy day with ice and slush on the roadway, a field sobriety test may be flawed. That’s because the road conditions can impact the driver’s ability to perform the test.

There are also many procedural requirements that apply to field sobriety tests. For example, there is certain protocol when a motorist momentarily stops while performing one of the tests that the police officer must follow.

To read more about field sobriety tests and whether or not they are reliable, see the Understanding the Field Sobriety Test page on our website.