Answer: There are three standardized field sobriety tests that officers are supposed to do prior to putting someone under arrest for operating while under the influence of an intoxicant. The first is the horizontal gaze nystagmus, which is essentially a test where they usually use a penlight to look and see where the eyeballs are jerking, to put it bluntly. And what they’re looking to see is whether or not the eyes can pursue smoothly, whether or not there’s an onset of jerkiness or nystagmus prior to 45 degrees and whether or not there’s distinct jerkiness or nystagmus at maximum deviation, when you hold the penlight all the way out by the shoulder. The second test would be the walk-and-turn, where a person’s asked to walk nine steps, turn around and come back, going heel to toe. The third test would be the one leg stand. That’s to see if you could hold your leg up for 30 seconds without putting it down. In a nutshell, they look at those tests to get a certain number of clues to determine whether or not those clues establish that someone is probably under the influence of an intoxicant.