The Standardized Field Sobriety Tests were developed by the National Highway Traffic Safety Administration to determine if you are impaired. Many tests were considered, but researchers decided three particular tests were the most accurate when considered together. The tests consist of the horizontal gaze nystagmus, walk and turn, and the one leg stand. These tests are meant to be administered in a standardized manner. The tests should be conducted on a flat, dry, level surface.
- Horizontal gaze nystagmus (HGN): The HGN is generally not admissible in Tennessee courts because there are many different causes of nystagmus other than alcohol or drugs. Even though the test is generally not admissible in Tennessee courts, it is important to determine if the test was administered properly. The test should be conduct in a specific manner and if the HGN is not, it could indicate lack of impairment.
- Walk and turn: The walk and turn test is a divided attention test. You are given a series of instructions that must be administered in the standardized fashion or the validity of the test can be compromised. If the validity of the test is compromised than it is not a good indicator as to whether you were impaired or not. Additionally, the officer does not tell you there are nine (9) clues he is looking for and if you demonstrate only two (2) clues, you have failed the walk and turn test.
- One leg stand: The one leg stand is the final divided attention administered during this three test battery. Like the other two tests, this test also has a standard series of instructions that must be administered or the validity of the test is compromised. Unlike the walk and turn, there are only four (4) clues in this test that the officer does not tell you about and the officer only needs to observe two (2) clues to make a determination that you are impaired and failed the test.
The officer can administer other non-standardized tests if you are unable to conduct the standardized test for medical reasons, weather conditions, or if you are over the age of sixty-five (65). Some of these standardized tests are: the finger count, finger to nose, modified romberg, and lack of convergence test.