Law enforcement officials throughout the nation are prohibited from making arbitrary arrests and subjecting individuals to searches and interrogations that are unfounded and without cause. In order to make an arrest for an alleged crime like DUI, they must collect evidence of their suspect's purported wrongdoing so that there are sufficient grounds on which to allege they have broken the law. In Virginia and other jurisdictions law enforcement officials use field sobriety tests and a means of getting evidence of drivers' suspected intoxication.
Field sobriety tests happen in real time during traffic stops. Drivers are asked to get out of their vehicles and are asked to perform several standardized physical tests. Based on their performances on these tests the drivers may be determined to be intoxicated and may then be arrested for alleged DUI.
Field sobriety tests assess drivers' balance, coordination and other physical capabilities. For example, during the walk-and-turn test a driver must walk in a straight line and return to where they started on the same path. If a driver wobbles or steps out to catch themselves then they may be assessed to be under the influence and a law enforcement official may have a piece of evidence against them.
However, field sobriety tests do not account for many of the individual qualities that may or may not make performing the tests easy for drivers. Drivers who suffer from medical conditions, who are taking prescriptions or who are simply asked to perform their tests on uneven ground may be disadvantaged. A field sobriety test may give bad information on a driver's state of intoxication and may support an arrest that is both wrongful and unjust.