How many clues must be present to indicate impairment during the HGN test?

In the Horizontal Gaze Nystagmus (HGN) test, the presence of four or more clues indicates impairment. This number is significant because it is based on the standardized criteria established for the test, which assesses the subject's eye movement as an indicator of intoxication.

Typically, the HGN test evaluates three specific indicators: the inability to follow a moving object smoothly, distinct and sustained nystagmus at maximum deviation, and onset of nystagmus prior to a 45-degree angle. Each of these indicators can yield clues about possible impairment. When an officer observes four or more total clues across these indicators, it provides substantial evidence suggesting that the individual may be under the influence of alcohol or drugs. This threshold makes the HGN test a reliable tool in the assessment of driving impairment, helping law enforcement make informed decisions regarding a suspect's sobriety.