When law enforcement officers pull someone over for suspected drunk driving and put him or her through a battery of tests at the side of the road, they aren't just making up things to amuse themselves or embarrass the driver. There is a Standardized Field Sobriety Test that consists of three individual tests to determine whether a driver is under the influence.
Research has shown that officers who are trained to perform SFSTs, which originated back in the 1970s, are able to correctly identify drunk drivers in more than 90 percent of cases. That's why they remain an integral part of most traffic stops involving suspected DUIs. Most states consider them admissible evidence in court.
The three tests that make up the SFST are:
-- Horizontal gaze nystagmus: The HGN shows involuntary jerking of the eyes when they follow an object from side to side. A person under the influence of alcohol usually has difficult time tracking a moving object smoothly.
-- Walk-and-turn: This tests a person's ability to walk in a straight line for a specific number of steps, touching the toes of one foot to the heel of the other, first in one direction and then the other. It's a test of being able to maintain balance and stay in a straight line while listening to the officer's instructions.
-- One-leg stand: This involves standing on one foot and counting from one thousand. Again, being able to maintain balance is key, as is the ability to count correctly and follow the officer's instructions.
Officers look for specific indicators of intoxication while drivers are performing these tests.
Of course, there may be any number of reasons why a driver, even if perfectly sober, can't perform one or more of these tests, including eye diseases and hearing impairment as well as balance and/or mobility issues. It's essential to make the officer aware of any reason why you might be unable to perform any of the tests.
Your attorney will look at any evidence, including the SFST, that is being used against you. He or she can work to dispute them if possible. However, don't try to perform these tests if you believe you're physically unable to and then try to explain to a judge or jury what happened.
Source: AAA DUI Justice Link, "Standardized Field Sobriety Test," accessed March 21, 2017