Today on 'Mornings With Ken and Bernie' Trooper Stephen Hammons, Public Information Officer with Troop I in Lafayette explained some of the procedures used by police to determine if someone is driving under the influence.

Hammons said,

I'm always amused when people ask if it's true when you're stopped for DUI you're asked to recite the alphabet backwards.  That is not true but there are three tests that are used.  The horizontal gaze test, the 'walk and turn' and the 'one leg stand' are all used.  The horizontal gaze test involves an officer moving an ink pen or finger from left to right and back across your line-of-sight.  A jerky eye movement would lead the officer to have you 'walk and turn' and the one leg stand because being under the influence will cause a person's eye movements to be jerky.

Trooper Hammons noted,

Before we start the field sobriety test we will question a person to determine if they have a condition that would prevent them from passing any of the testing.  A person with a knee or ankle injury might not be able to successfully complete a 'walk and turn' or the one leg stand.

According to Hammons there are other signs of possible impairment including,

Slurred speech, red water eyes, odor of alcohol all usually tell an officer he should conduct a field sobriety test.

Trooper Hammons goes on to discuss blood-alcohol testing and the associated jail terms associated with a refusal to submit to testing.  You can hear the entire discussion by listening to the interview: