When you are stopped by a police officer who suspects that you are operating your vehicle while intoxicated, the officer will likely do a field sobriety test on you. There are several different field sobriety tests that can be used, but there is only one Standardized Field Sobriety Test.
The SFST consists of three different tests. The tests are administered in a specific manner to determine if a person is intoxicated. When the SFST is administered as intended, it is said to be 91 percent accurate.
The first test in the battery of tests is the horizontal gaze nystagmus test. The law enforcement officer has you follow an object that is moving slowly. You can only use your eyes. The officer looks to see if your eyes have a jerking motion as you follow the object. Jerking in your eyes that meets certain markers can indicate intoxication.
The second test in the battery of tests is the walk and turn, which involves walking in a straight line heel-to-toe while then turning around and walking the same way back to the starting point. This test is considered a divided attention test that included mental tasks and physical tasks. A person who is intoxicated usually can't complete the test without difficulty because of the divided attention it requires. This test has eight markers of impairment that the officer looks for.
The third test is the one leg stand. In this test, which is also a divided attention test, you have to stand on one leg with your other foot off the ground. You also have to count while you balance. This test has four markers the officer looks for that would indicate impairment.
If you are stopped for the suspicion of drunk driving, it is important that you know your rights. Understanding the process might help you as you go through it. Above all, remember that you have the right to legal representation before you answer any questions.
Source: National Highway Traffic Safety Administration, "Standardized Field Sobriety Testing," accessed April. 23, 2015