Interviewer: What is the purpose of the field sobriety test?
Court Koehler: The National Highway Traffic Safety Association did a study some years ago – a while ago, maybe a couple decades. They basically formulated these field sobriety tests and they’re supposed to give officers clues as to whether or not a person is intoxicated or not able to safely drive a vehicle. They’re kind of loosely based on science. They’re not necessarily as accurate scientifically as we think they are. They’re very specific about the way that they have to be performed and the sorts of things that they do. It makes people think that they are a sort of failsafe, scientific ways of telling is somebody is drunk or not.
But really they are just studies that say when a person exhibits this or that clue, it tends to show that they may be intoxicated. What the police officers use them for is they use them to develop probable cause to put you under arrest for a DUI So when they are giving you field sobriety tests is they’re just, it’s not a test really that you pass or fail; it’s just an opportunity for the officer to gather evidence that they can use to develop a probable cause statement, sufficient enough for them to arrest you for DUI
Interviewer: At what point is it administered?
Court Koehler: They have to have some sort of a reason to suspect that you are driving under the influence before they can stop you, because otherwise it’s unconstitutional. Probably most people know you can’t be unreasonably searched or seized and if an officer were to stop you and make you do field sobriety test for no reason, that would be considered an unreasonable seizure. So what they need to have before they can do the field sobriety test, according to the legal standard, is a reasonable, articulable suspicion that you are driving under the influence. What that amounts to is usually things like they will say they smelled alcohol coming from the car; they might say the driver’s speech was slurred or slow. They might say their face was flushed or their eyes were bloodshot.
They can also use driving clues, such as improper lane changes, driving with your lights off or speeding. These things are theoretically clues that you are driving under the influence that sort of gives them the amount of suspicion that they need legally to then detain you and give you field sobriety tests.