If you are like most people in North Carolina, you are aware that before a person is arrested for suspected drunk driving, they are commonly asked to take certain tests at the site where they were initially stopped by officers. These tests are called field sobriety tests and while the outcome of the tests may influence whether or not a person is charged with a driving while intoxicated offense, they cannot actually prove that a person is impaired.
As explained by FieldSobrietyTests.org, there are three tests approved for use by the National Highway Traffic Safety Administration. None of these tests are able to prove that a person is drunk or even to determine a level of intoxication. Instead, the purpose of the field sobriety tests is simply to gather enough evidence to show that a driver might possibly be impaired. This evidence is then used to support an arrest. In a way, you can think of it like probable cause.
It is also important for a driver to know that each of the three field sobriety tests has a known level of inaccuracy. Individually, the test accuracy rates range from a low of 65 percent for the one-leg stand test to a high of only 77 percent for the horizontal gaze nystagmus test.
This information is not intended to provide legal advice but is instead meant to give residents in North Carolina information about the field sobriety tests used during a drunk driving investigation so they understand what these tests can and cannot prove.