Which of the following tests remains the most reliable of the 3-test battery?

The Horizontal Gaze Nystagmus (HGN) test is considered the most reliable of the three tests in the Standardized Field Sobriety Test (SFST) protocol, and this reliability stems from its ability to produce measurable and observable indicators of impairment. HGN assesses the involuntary jerking of the eyes as they follow a moving object, which becomes more pronounced with the consumption of alcohol and certain drugs. This physiological response can be objectively evaluated, making it less subjective than other tests.

The validity of HGN lies in its strong correlation with blood alcohol concentration (BAC) levels, particularly at 0.08% or higher, which is the legal limit in most jurisdictions. Many studies support its effectiveness, demonstrating that trained officers can accurately identify impaired drivers based on the results of this test.

In contrast, while the Walk-and-Turn (WAT) and One-Leg Stand (OLS) tests provide valuable insights into a subject’s physical coordination and balance, they are more subjective and can be influenced by various factors, such as nerves, weather, or pre-existing medical conditions. These factors can make it more challenging to draw definitive conclusions about a person’s impairment based solely on their performance on those tests. Thus, HGN stands out