Being stopped on suspicion of impaired driving can be a stressful experience. During these encounters, law enforcement officers often rely on field sobriety tests as part of their investigation.
Many drivers are surprised to learn that these tests are not always as straightforward as they appear. A variety of physical, environmental and personal factors can influence a person’s performance.
Common types of field sobriety evaluations
Field sobriety tests are designed to help officers assess whether a driver may be impaired by alcohol or drugs. The three standardized field sobriety tests commonly used by law enforcement are the Horizontal Gaze Nystagmus (HGN) test, the Walk-and-Turn (WAT) test and the One-Leg Stand (OLS) test.
The HGN test evaluates involuntary eye jerking that may become more pronounced after alcohol consumption, while the WAT and OLS tests assess a person’s balance, coordination and ability to follow instructions. During the WAT test, the person is typically instructed to take heel-to-toe steps along a straight line, and during the OLS test, they must stand on one foot approximately six inches off the ground while counting aloud for about 30 seconds.
While these tests are widely used, performance can be affected by many factors unrelated to alcohol or drug use. Medical conditions, injuries and even certain medications may make it difficult for someone to successfully complete the tasks. Age and physical limitations can also play a role.
Additionally, environmental conditions may further impact results. Uneven pavement, poor lighting and bad weather can make balancing or following instructions more challenging. Anxiety and nervousness during a traffic stop may also affect a person’s ability to perform.
Because field sobriety tests involve a degree of subjective interpretation, questions sometimes arise regarding their accuracy and reliability. An officer’s observations, combined with other evidence gathered during a traffic stop, may become important factors in a DUI or drug-related driving case. Understanding the circumstances surrounding the testing process can be essential when evaluating the strength of the evidence.
If you are facing an impaired driving charge, it is helpful to discuss your situation with a legal professional who can review the facts of your case, explain your options and help protect your rights moving forward.
