Field sobriety tests, or FSTs, are a critical part of a DUI arrest. If an officer suspects that a motorist may be intoxicated, the officer nearly always asks the driver to perform these agility tests. These tests also indicate whether or not a person is mentally impaired.
There are a number of FSTs, but only three have been approved by the National Highway Transportation Safety Administration. The arresting officers always say that the defendants failed the tests, and therefore they were arrested. By challenging the results, an attorney may be able to show that there was no probable cause for a DUI arrest and a case may be thrown out.
Horizontal Gaze Nystagmus
Most people are familiar with the HGN test. The test administrator, who is nearly always the officer, asks the subjects to follow a point with their eyes without moving their heads. The point is usually the tip of an ink pen in daylight hours and a flashlight at night. Nystagmus is an involuntary eye jerk. If there are four or more clues between the two eyes, the subject may have a BAC of at least .08....