During the HGN test, what signifies that a subject may be over the legal limit for alcohol?

The Horizontal Gaze Nystagmus (HGN) test is designed to assess if a person may be impaired by alcohol or other substances. During this test, an officer looks for specific clues that indicate a potential level of intoxication. The presence of two or more clues, such as distinct and sustained nystagmus at maximum deviation or an angle of onset of nystagmus prior to 45 degrees, suggests that the individual may be over the legal limit for alcohol.

These clues are critical as they are scientifically validated indicators of impairment. The HGN test is based on the physiological effects of alcohol on the nervous system, which can affect eye movement. When an individual shows two or more specific signs during the test, it strongly indicates that their blood alcohol concentration (BAC) may be at or above the legal threshold.

Other options such as slurred speech or slow reactions are common signs of intoxication but are not part of the HGN test specifically and thus aren't utilized to determine impairment within that test context. Visible eye tremors alone do not provide the same level of evidence as the precise scoring of the HGN test; therefore, they don’t carry the same weight as the measurement of clues found during the structured evaluation of the HGN