Normally, Standardized Field Sobriety Tests are given by police officers as part of their DUI investigation. They usually consist of a Horizontal Gaze Nystagmus (HGN) test, a Walk-and-Turn test and a One Leg Stand test.
The HGN test typically involves an officer passing a stimulus, often a penlight, back-and-forth in front of a person's eyes. The person is supposed to follow the stimulus with both eyes. The officer is trying to observe an "involuntary jerking" of the eye which can be visible if someone has had too much to drink. There are other sources of HGN, including anti-depressants, other drugs, natural nystagmus, and other causes.
These two tests are supposed to test a person's "divided attention" skills. When driving a vehicle, a person has to simultaneously undertake physical actions while mentally processing information. The Walk-and-Turn and One Leg Stand test involve physical movement and mental processing, so the idea is that how a person does on these tests will indicate if a person is capable of driving or impaired.
The tests have limited usefulness. People have different physical and mental capabilities that will influence the outcome. For example, some people are athletic and others have poor balance. Some people are nervous about taking a test in front of the police, and others are poised. The same test is given to a 25-year-old and a 63-year-old: Who is going to be more agile?
If you have questions about how you did on these tests, please make an appointment to discuss your case.