Police officers have several ways to determine if a driver is impaired during a traffic stop. One of these is the use of sobriety tests. While there are many performed across the country, there are only three specific tests that comprise the standardized field sobriety test. This battery of tests is endorsed by the National Highway Traffic and Safety Administration.

When these three tests are used together, they are supposed to accurately indicate whether a driver is impaired approximately 91% of the time. While some argue that this still leaves a large error margin (and some argue that the accuracy isn’t nearly that high), this battery of tests is admissible in court.

• Walk-and-turn: You have to take nine steps placing your feet heel-to-toe while remaining in a straight line. Once you take nine steps, you use one foot to turn and go back the other way using the heel-to-toe method.
• Horizontal gaze nystagmus: Alcohol impairment can cause changes in the natural jerking of the eye that occurs when you divert your eyes to the side. The officer asks you to look at an object and follow it using only your eyes. While you do this, they look for eye jerking at various points of the eye’s glide from the front to the side and back.
• One-leg stand: You have to stand on one foot for 30 seconds. The foot that’s off the ground is elevated approximately six inches. Having to hop, put your foot down or using your arms to balance are considered signs of impairment.

These tests must be performed in a very specific manner. Any deviations can lead to skewed results. If you’re arrested for drunk driving and the officer did a field sobriety test, your attorney might be able to use information about what happened as part of your defense.