Law enforcement officers use field sobriety tests to assist them in determining whether you are driving under the influence of alcohol. You will take the test on the side of the road after a traffic stop.
FindLaw explains that you will usually take field sobriety tests prior to a breath test. There are three parts.
Walk and turn
To do this test, the officer will instruct you to take nine steps forward. As you walk, you must touch your heel to your toe. You will then turn around and walk the same way back to the officer.
You will fail if you cannot complete the walk or if you are having balance issues at any point during the instructions or the completion of the test.
You will need to stand on one leg and count out loud, beginning at 1000. You will need to keep your foot up and keep counting until the officer tells you that you are finished.
If you mess up the counting or cannot maintain your balance, you will fail. Putting your foot down at any time or failing to follow the instructions may also result in a fail.
Horizontal gaze nystagmus
This test is more scientific than the others and is involuntary. In this test, the officer will have you track an object, such as a finger or a pen, that he or she holds out in front of your face with your eyes. The officer will watch how your eyes respond. If you cannot smoothly follow the object, then you fail the test.