What is the main focus of field sobriety tests like HGN, Walk and Turn, and One Leg Stand?

Field sobriety tests, such as the Horizontal Gaze Nystagmus (HGN), Walk and Turn, and One Leg Stand, are designed primarily to assess physical coordination and balance. These tests evaluate an individual's ability to perform specific physical tasks that can indicate impairment. For example, the HGN test looks for involuntary eye movements that typically become more pronounced under the influence of alcohol or drugs, while the Walk and Turn and One Leg Stand tests assess balance, coordination, and the ability to follow instructions—all of which can be negatively affected by substances.

Effectively, these tests are used by law enforcement officers during DUI stops to gather observable evidence of impairment. By focusing on physical coordination, officers can make informed decisions about whether to pursue further testing, such as breath or blood tests, to confirm the presence of alcohol or other substances in the driver's system.