What does nystagmus refer to in the context of a DUI investigation?

Nystagmus refers to the involuntary jerking or twitching movements of the eyes. In the context of a DUI investigation, officers often examine a person's eye movements as part of field sobriety tests. When a person is under the influence of alcohol or certain drugs, their eye muscle control can be impaired, leading to noticeable jerking. This can be particularly evident when the eyes are moved slowly from side to side or up and down.

Detecting nystagmus is important because it provides an observable indicator that may suggest impairment. Officers are trained to recognize these jerking movements as they can indicate elevated blood alcohol content or the influence of drugs, thus forming part of the evidence that supports a DUI charge. Understanding the physiological responses of the eyes under the influence is critical for field sobriety evaluations, making the identification of nystagmus a key component of DUI investigations.