Being pulled over by a police officer for the suspicion of drunk driving triggers a variety of steps that will likely occur during the traffic stop. Once the officer has a chance to speak to the driver, they may decide to ask them to take a field sobriety test.
Not all field sobriety tests are equal. There is only one battery of tests, the standardized field sobriety test, that’s endorsed by the National Highway Traffic Safety Administration. The three tests included are the only ones that are considered reliable enough to be admissible in court.
Horizontal gaze nystagmus test
The HGN test checks for involuntary jerking of the eyes, called nystagmus, which becomes more pronounced when a person is under the influence of alcohol or certain drugs.
During this test, the officer holds a small object, like a pen or flashlight, about 12–15 inches in front of the driver’s eyes. The officer slowly moves the object side to side, watching the driver’s eyes as they follow it.
One-leg stand
The one-leg stand test assesses balance and focus, as divided attention can be difficult for someone who’s impaired. Officers look for swaying, hopping, putting the raised foot down, or using arms for balance as clues of possible impairment.
Walk and turn
This test checks balance, coordination, and the ability to follow instructions—skills that alcohol can impair. During this test, the officer watches for signs of impairment, like stepping off the line, using arms for balance, taking the wrong number of steps, stopping in the middle, or failing to follow instructions properly.
Anyone who’s facing a drunk driving charge should explore their options for a defense. In some cases, that might include calling the administration or interpretation of the standardized field sobriety test into question. Having experienced legal guidance can be beneficial in determining the most appropriate defense strategy for your needs.