Field Sobriety Test (FST) Law and Legal Definition

Field Sobriety Tests are evaluations done by law enforcement officers in making roadside determinations as to whether a motorist is under the influence of alcohol or drugs. Through the performance of these tests or evaluations, the officer subjectively determines how the motorist reacts to and performs the requested tasks. It helps the officer to determine whether or not it is appropriate to arrest the person. Motorists suspected of DUI / DWI is routinely asked by police officers to perform one or more field sobriety exercises. A motorist's alleged poor performance on field evaluations may provide the "probable cause" an officer needs to arrest a person for impaired driving and may also become part of the proof roadside alcohol screening tests used to later convict the person at trial. [Parrish v. State, 216 Ga. App. 832, 833-834 (Ga. Ct. App. 1995)]

Standardized field sobriety tests [SFSTs] were designed back in 1970’s pursuant to numerous federal grants and ultimately sanctioned by NHTSA (the National Highway Traffic and Safety Administration) beginning in 1984. The three tests used are (1) the walk and turn [WAT] test, (2) the one leg stand [OLS] test, and (3) the horizontal gaze nystagmus [HGN] test.