What percentage of the time can the HGN test determine if a suspect's BAC is above 0.10?

The Horizontal Gaze Nystagmus (HGN) test is a key component of the Standardized Field Sobriety Test (SFST) used by law enforcement to assess potential impairment due to alcohol. Research has shown that the HGN test is particularly effective in detecting elevated blood alcohol concentrations (BAC), specifically above 0.10.

A correct identification rate of approximately 77 percent indicates that when a suspect has a BAC above this threshold, the HGN test can accurately identify the impairment in a significant majority of cases. This reliability stems from the physiological effects of alcohol on eye movement, which are identified through the test, making it a credible measure of impairment.

This percentage aligns with established research findings within the realm of SFST, validating the HGN test's effectiveness as a tool for law enforcement officers when assessing drivers suspected of alcohol impairment.