Fst (see Also Field Sobriety Test)

FST or field sobriety test is a common test used by United States law enforcement officers to evaluate a driver's mental and physical coordination and whether or not the driver is operating a motorized vehicle under the influence of drugs or alcohol. Field sobriety tests have been standardized to include the walk-and -turn test, the one-leg-stand test and the horizontal gaze nystagmus test.

Although the standardized field sobriety test is subjective, the National Highway Traffic and Safety Administration has concluded that if it is performed according to the correct outlined testing procedures by a trained professional it can help law enforcement officers determine if a driver is under the influence of alcohol.

Most states allow drivers to refuse to take a standardized field sobriety test but do penalize drivers who refuse a blood alcohol concentration test. Officers must have probable cause to make a DUI stop and perform a field sobriety test. If an individual is overweight, aged or has certain mental or physical disabilities they may have difficulty performing the FST even if they are completely sober.