There are three major types of field sobriety tests that police officers use to determine a driver’s sobriety in Pennsylvania. The Standard Field Sobriety Test (SFST) is a series of three tests: the horizontal gaze nystagmus, the walk-and-turn and the one-leg stand.
Horizontal gaze nystagmus test
The horizontal gaze nystagmus test occurs when the person’s eyes follow an object that moves from side to side. The eye is supposed to jerk involuntarily when it moves to the side. This jerking movement is increased when a person is intoxicated. The eyes cannot follow the object easily, and jerking occurs at angles within 45 degrees.
Walk-and-turn test
A walk-and-turn test allows the officer to check a person’s balance. An intoxicated driver has difficulty walking in a straight line and making smooth turns. The person is asked to walk heel to toe on a straight line in forward and opposite directions. Signs of impairment include not walking on the straight line, not following instructions, not walking heel to toe and wobbling on the line.
One-leg stand test
The one-leg stand test requires that the person stand on one leg several inches above ground and count up from 1,001 until the officer says to stop. Signs of drunk driving include falling over, putting the leg down more than once and moving side to side to remain steady.
Field tests for drunk driving
The horizontal gaze nystagmus, the walk-and-turn and the one-leg stand tests are national standards for testing a driver’s level of intoxication without using a device. Each test has a 50% or higher accuracy rating. The SFST is fast, easy and recommended to perform before the blood alcohol concentration level is calculated.