Nevada Field Sobriety Tests Explained

Only three field sobriety tests are "standardized," meaning NHTSA has published a fixed way to administer and score them: the Horizontal Gaze Nystagmus, the Walk-and-Turn, and the One-Leg Stand. Officers look for specific "clues," and even the validation studies behind these tests report meaningful error rates when conditions are good — let alone on a dark, uneven Las Vegas roadside.

Any deviation from the standardized procedure undermines the result. If the officer rushed the instructions, demonstrated incorrectly, or scored clues that were not there, the test loses its value as evidence.

It is important not to confuse the voluntary roadside tests with the post-arrest evidentiary breath or blood test. The field sobriety tests and the handheld preliminary breath test happen before arrest and are voluntary. The evidentiary test happens after a lawful DUI arrest and is required under Nevada's implied-consent law — refusing it carries real consequences.

In other words, you can decline to balance and walk on the roadside, but once lawfully arrested you cannot lawfully refuse the official breath or blood test.

These tests assume a healthy, calm person on a flat, well-lit surface in good shoes — conditions that rarely exist at a real traffic stop. Inner-ear and balance disorders, back, knee, and ankle injuries, obesity, age over 65, anxiety, flashing patrol lights, traffic noise, wind, cold, and uneven pavement all generate the same "clues" an officer reads as impairment.

Non-standardized tests — reciting the alphabet, counting backward, the finger-to-nose test — are even less reliable and are not part of the validated battery at all. A DUI defense attorney can often show the "clues" came from the conditions, not from alcohol.