Which of the following is a validated field sobriety test?

The correct answer, which is the one leg stand test, is recognized as a validated field sobriety test. This particular test measures a person's ability to maintain balance while following instructions, which correlates with their level of impairment. During the test, the subject is asked to stand on one leg for a certain amount of time while counting. Observations are made regarding the individual's ability to stay upright without swaying, using their arms for balance, or putting their foot down.

The reliability of the one leg stand test in detecting alcohol impairment contributes to its selection as a standard sobriety measure used by law enforcement. Its established guidelines and clear scoring enable officers to assess a suspect's balance and coordination, both of which are key indicators of sobriety.

While other tests like the horizontal gaze nystagmus and walk and turn are also validated tests for detecting impairment, the emphasis is on the one leg stand as the answer in this context. The finger-to-nose test, on the other hand, while used in practice, lacks the same level of validation and structured guidelines in the context of field sobriety assessments.