Field Sobriety Tests in Nevada: What Officers Look For and How to Challenge the Results

Anyone pulled over has a good chance of being asked to step out of the vehicle and perform a series of physical tasks. These are field sobriety tests, and they play a bigger role in DUI cases than most people realize. What’s worse is that these tests aren’t as objective or reliable as they might appear.

The 3 Standardized Tests

Police officers and sheriff’s deputies in Nevada use three tests developed by the National Highway Traffic Safety Administration (NHTSA) to help determine a driver’s sobriety.

• The Horizontal Gaze Nystagmus (HGN) test involves the officer holding a small light or pen in front of the person’s face and moving it slowly from side to side while watching their eyes. They’re looking for an involuntary jerking of the eye (called nystagmus), which can be caused by alcohol impairment. Officers are trained to check whether the eye tracks smoothly, if the jerking begins before the eye reaches a 45-degree angle, and whether it becomes pronounced at maximum deviation.
• The Walk-and-Turn test involves taking nine heel-to-toe steps along a straight line, turning on one foot, and returning. Officers look at whether the person steps off the line, uses their arms for balance, takes the wrong number of steps, or starts before the instructions are finished.
• The One-Leg Stand requires lifting one foot about six inches off the ground and counting aloud while balancing. Officers look for swaying, using arms for balance, hopping, and putting the foot down.

NHTSA’s research states that when all three tests are used together, they correctly identify impairment only about 72% of the time.

Why the Results Can Be Challenged

A human officer operating in the field scores sobriety tests, often at night, on uneven pavement, after the stress of a traffic stop, which means errors are inherent.

Many factors can create “clues” of drunk driving that have nothing to do with alcohol. Inner ear problems, neurological issues, leg or back injuries, and even fatigue can affect balance and eye movement. Prescription medications interfere with HGN results, and age and weight can affect performance on the Walk-and-Turn and One-Leg Stand.

The testing environment matters, too. Performing a balance test on a sloped road shoulder, in poor lighting, in heels or dress shoes, or while stressed and disoriented from a traffic stop is not the same as doing it under controlled conditions.

Officers also have to follow specific NHTSA protocols for administering each test. If they deviate, that can skew the results.

What Does This Mean for a Defense?

Field sobriety tests are major evidence in a DUI case, but they’re not perfect. An experienced DUI defense attorney will examine the officer’s training records, the dashcam or bodycam footage of the stop, and the specific conditions under which the tests were administered.

If you’ve been charged with DUI in Las Vegas, don’t assume the field sobriety test results seal your fate. Contact CEGA Criminal Law Group today.