What is the significance of the HGN test in assessing impairment?

The Horizontal Gaze Nystagmus (HGN) test is significant in assessing impairment because it is highly effective in detecting signs of alcohol intoxication and can indicate a higher level of impairment. The HGN test involves assessing the involuntary jerking of the eyes as they follow a moving object, typically a pen or flashlight. When a person is impaired by alcohol, the onset of nystagmus occurs at lower angles and may manifest more pronouncedly than in a sober person.

This characteristic makes the HGN test particularly valuable, as it provides law enforcement with a reliable indicator that can be correlated with Blood Alcohol Concentration (BAC) levels. Research has shown that a certain degree of HGN is prevalent among individuals with a BAC of 0.08% or higher, which is the threshold for legal intoxication in many jurisdictions. By identifying these eye movement changes, officers can effectively assess the level of impairment due to alcohol, making the HGN test a crucial tool in DUI evaluations.

The other options do not capture the core importance of the HGN test in the context of assessing intoxication levels.