The Standardized Field Sobriety Test (SFST) is a battery of tests administered by police officers when they have stopped a motor vehicle driver and suspect the driver is driving under the influence of alcohol or drugs. The SFST include (1) the horizontal gaze nystagmus (HGN) (the “follow my finger test”); (2) the one-leg-stand test; and (3) the walk-and-turn test.

There are also non-standardized field sobriety tests commonly given by police officers, including (1) the Rhomberg balance test; (2) the finger-to-nose test; (3) the ABC test; (4) the hand-pat test; (5) the numbers-backward test; and (6) the finger-count test or finger-tap test. Because these tests are non-standardized they generally carry less weight in court, but may serve as a basis for the police officer’s subjective determination that the driver is intoxicated, and the driver’s subsequent arrest.

The SFST are recommended by the National Highway Traffic Safety Administration and are generally admissible in court—but the police officer who administered the HGN test must be qualified to administer it (with certification from a training course) for the related videotape and testimony to be admissible at trial. In contrast, police officers generally may only testify as lay witnesses (not experts) regarding the one-leg-stand and walk-and-turn tests.

A person who is suspected of driving under the influence of alcohol or drugs may be asked to submit to these field sobriety tests. Some states have implied-consent laws (statutes) stating that by applying for and accepting a driver’s license issued by the state the driver consents to such tests when requested by a police officer. But a driver generally may refuse to participate in such tests (without explanation), as forced tests (1) may violate a person’s Fifth Amendment right not to be compelled to testify against oneself, and (2) may be of questionable reliability in determining intoxication.

In some states, refusing to engage in field sobriety tests has consequences, including (1) admission of the refusal in evidence at trial; (2) fines and penalties; and (3) automatic driver’s license suspension.

In Texas, the Standardized Field Sobriety Test (SFST) is commonly used by law enforcement to determine if a driver is under the influence of alcohol or drugs. The SFST includes the horizontal gaze nystagmus (HGN), the one-leg-stand test, and the walk-and-turn test. Texas courts generally allow the results of these tests as evidence, but the officer administering the HGN must be properly trained and certified for the results to be admissible in court. Non-standardized tests such as the Rhomberg balance test and the finger-to-nose test are also used but carry less weight in court. Texas has implied consent laws, meaning that drivers have implicitly agreed to submit to sobriety tests by accepting a Texas driver's license. However, drivers can refuse to participate in field sobriety tests. Refusal to take the tests can lead to consequences such as the introduction of the refusal as evidence at trial, fines, penalties, and automatic driver's license suspension. It's important to note that forced participation in these tests may raise constitutional issues under the Fifth Amendment, which protects against self-incrimination.