Field sobriety tests (FST) are groups of three tests employed by law enforcement to determine if the driver is under the influence of drugs or alcohol. If the driver fails one of the three tests, the officer then asks the driver to take a breathalyzer or a chemical test to confirm their blood-alcohol content. The tests administered by a trained officer are 90% successful in determining if the driver is impaired by alcohol. The prosecution can then use the results in court as evidence to convict the driver.
The three tests
These tests measure balance, coordination and the ability to do more than one task at once:
- Horizontal Gaze Nystagmus: This involves the eyes tracking the periphery movement of a light or pen. The eyes will jump when at high periphery levels rather than smoothly tracking. The jumps are more pronounced at a lower onset of 45 degrees in intoxicated individuals.
- Walk and turn: The driver takes nine heel-to-toe steps along a straight line. Then, they turn on one foot and return in the same fashion. Common indicators are the inability to keep balance while listening, starting before instructions are complete, not touching heel to toe, incorrect number of steps, or loss of balance. Officers look for two or more indicators.
- One-legged stand: The other foot is held six inches off the ground while the individual counts backward from 1,001. The test lasts about 30 seconds. Officers look for hops to correct balance, swaying while balancing, putting the raised foot down, or using arms for balance. Officers look for two or more indicators.
What can the driver do
Drivers can refuse to take these or subsequent tests, but it violates the state’s implied consent laws and comes with penalties. These tests are by no means easy to pass when sober, and the officer may not follow proper protocols for administering the test. Drivers should try to remain calm. They can also seek a criminal defense attorney representing those accused of DUI. These legal professionals understand how these tests work and can point out irregularities that can weaken the strength of the officer’s evidence.