How do police officers perform a field sobriety test?


In order to arrest you for suspected impaired driving, officers need to have some sort of evidence of potential chemical intoxication. During a traffic stop where officers suspect someone of driving under the influence (DUI) because of erratic driving behavior, the officers need to interact with the driver to determine if they have probable cause to request a chemical breath test and possibly arrest them.

After initially talking with the driver, performing a field sobriety test is often the second step in the process of moving from a traffic stop to a DUI arrest. Understanding the various tests that officers perform can help you better understand how they demonstrate impairment and if you can push back against the officer’s claims.

Some of the tests look at issues like memory, balance and speech

The most well-known field sobriety test is probably either the walk-and-turn test or the balance one-leg stand test. In a walk-and-turn test, a driver needs to walk in a straight line, turn 180 degrees and then walk in a straight line back for the officer.

In a one-leg stand or balance test, the officer may have an individual stand on one foot. Officers can also interact with drivers verbally to look for signs of impaired cognitive functions, such as difficulty remembering information or reaching logical conclusions.

Unfortunately, with both of these tests, the potential exists for someone with a medical condition to fail the field sobriety test and wind up arrested. Additionally, individuals who habitually drink could practice balancing on one leg, walking and turning, or even reciting the alphabet backward while drunk in order to do better during a field sobriety test.

Officers will also check your eyes for involuntary movement

Given that there is potential for officers to wrongly arrest someone because of medical conditions that affect speech or motor function, one of the most important tests in the field sobriety test is arguably the horizontal gaze nystagmus test.

Unlike many of the other standard tests, it is impossible for someone to practice for a gaze test. The motion in someone’s eyes while they are under the influence of alcohol is an involuntary response. Officers will look for a movement of the eye when someone turns their gaze to the side and watch for jerky motions, which occur because of the bodily response to alcohol.

If you have medical conditions or other explanations that could reasonably explain why you struggle with a field sobriety test, this could potentially help you defend yourself against pending charges related to a recent traffic stop that involved a failed field sobriety test.