What is the purpose of observing distinct and sustained nystagmus?

Observing distinct and sustained nystagmus serves the critical purpose of identifying maximum eye deviation, which is an important indicator in assessing potential impairment during DUI investigations. Nystagmus refers to involuntary eye movement that can manifest as a result of intoxication or certain medical conditions.

In the context of a DUI traffic stop, law enforcement officers often look for the presence of nystagmus as it can reveal whether an individual's motor control and coordination are compromised due to alcohol or drug use. The distinct and sustained nature of nystagmus specifically refers to the eyes jerking in a manner that is not only noticeable but remains constant when the eyes are held in a position at the edge of their range of motion.

This observation is significant because it helps officers evaluate the driver's level of impairment, as the presence of maximum eye deviation can suggest a higher blood alcohol concentration. Understanding this physical sign assists officers in making informed decisions during their assessments.