In the San Diego SFST validation studies, which test was determined to be the most accurate in identifying a person with a BAC level of 0.08% or higher?

The Horizontal Gaze Nystagmus (HGN) test was identified in the San Diego SFST validation studies as the most accurate for determining a person with a Blood Alcohol Concentration (BAC) of 0.08% or higher. This test evaluates the presence of nystagmus, which is an involuntary jerking of the eyes that becomes more pronounced with alcohol consumption. The methodology involves observing the eyes as they follow a stimulus, typically a pen or finger, through a full range of motion.

The reliability of HGN lies in its ability to measure physical indicators of impairment. Research demonstrated that HGN could successfully predict BAC levels with high accuracy, distinguishing it from other field sobriety tests which, while also useful, may not provide the same level of specificity or correlation to precise BAC levels.

The other tests, such as Walk and Turn and One Leg Stand, while effective in assessing balance and coordination, focus more on functional physical capabilities rather than directly measuring the physiological effects of alcohol on the eye’s function. The Breathalyzer Test, although useful for quantifying BAC, is not considered a part of the field sobriety testing process and is a separate method of BAC assessment typically used after the initial sobriety evaluations. Therefore,