If a law enforcement officer pulls you over while driving, they might ask you to take field sobriety tests. These tests are not scientific. Rather, the police use them to make a subjective assessment of your apparent drunkenness based on how they think you’ve performed.
There are many versions of these tests, but the National Highway Traffic and Safety Administration (NHTSA) only officially recognizes three. The combined results of these three tests can give a pretty accurate understanding of whether someone is drunk or not. These tests are not infallible, though. If you are ever subjected to these tests, this is what you can expect.
Horizontal gaze nystagmus
The officer will hold an item in front of your face and move it around. You will have to keep staring straight at it. They are checking to see if your eyes make unexpected movements, which they could well do for many reasons other than drunkenness.
Walk and turn
In this test, you have to walk heel to toe along a straight line (often the centerline on the road). It sounds easy, but many things could cause you to fail even when sober, such as a disability, uncomfortable shoes or the ground being baking hot.
One-legged stand
This involves you balancing on one leg. Again, it is not as easy as it sounds – some people just have awful balance, perhaps due to an inner ear issue. Others fail due to nerves.
It’s best to politely refuse these tests. Officers cannot make you take them, and a court cannot punish you for doing so. There are so many reasons you could fail these tests that it is not worth the risk, as failing makes it more likely that the police will arrest you.