If police officers believe that drivers are under the influence, they may conduct traffic stops. After talking to a driver, they may ask the motorist to perform field sobriety tests. Officers ask motorists to step out of their vehicles and follow a series of instructions.
Depending on what happens during the testing, the driver may proceed to their destination or may end up facing driving while intoxicated (DWI) charges. Drivers who know what to expect may be in a better position to navigate an impaired driving traffic stop and respond to a request for field sobriety testing.
There are standardized field sobriety tests
Sometimes, the popular media turns field sobriety testing into a punchline. They depict police officers guiding people through nonsensical actions at the side of the road. The reality is far more banal and predictable. Officers must perform specific types of tests that have a degree of scientific credibility. Field sobriety testing has a high rate of false positives, but the three standardized tests are considered moderately reliable.
The first test is a walk-and-turn test. Police officers instruct drivers to walk in a straight line, turn 180° and follow the same line back toward the officer. They may also have the driver perform the one-leg stand test. During this test, drivers must shift their balance to one leg.
Both the way that people walk and the way that they balance can change when they are under the influence of alcohol. Officers typically conduct these tests in locations where they can record video footage in addition to taking notes about the driver’s performance.
The final field sobriety test is the horizontal gaze nystagmus test. This test involves a driver following a pen, light or finger with their eyes. They keep their heads still and only move their eyes from side to side. Officers watch for visible muscle spasms in the eyes that alcohol strengthens.
Technically, drivers can fail one or all of these tests due to reasons other than chemical impairment. Field sobriety testing is therefore only one component of a successful drunk driving case. Still, motorists stopped for suspicion of DWI offenses may want to decline field sobriety testing, which is legally within their rights. Drivers who refuse to perform field sobriety tests are not at risk of summary arrest or additional penalties.
The rules about mandatory testing only apply to post-arrest chemical tests. Responding effectively during a DWI traffic stop can make a major difference for a driver. Motorists who understand field sobriety testing and their rights can limit their risk of unfair criminal charges.