Standardized field sobriety tests (SFST) are resources used by law enforcement to assess whether a driver is under the influence of alcohol or drugs. These tests are standardized per the National Highway Traffic Safety Administration.
Understanding these tests is crucial. These are the only three tests that are recognized as SFSTs. If you choose to participate in them, know that they may be used as evidence against you, even if you are sober at the time of testing.
Horizontal Gaze Nystagmus
The HGN test involves an officer observing a suspect’s eyes as they follow a moving object, usually a pen or flashlight, horizontally with their eyes. The officer looks for signs of nystagmus, an involuntary eyeball jerking that occurs naturally as the eyes rotate at high peripheral angles.
Walk-and-Turn Test
This test assesses a subject’s ability to complete tasks requiring physical and mental concentration. The individual is instructed to take nine steps, heel-to-toe, along a straight line, turn on one foot and return in the same manner.
During the test, officers look for indicators of impairment, such as:
- Being unable to keep balance
- Starting before instructions are finished
- Stopping while walking to regain balance
- Failing to touch heel-to-toe
- Stepping off the line
- Using arms to balance
- Making an improper turn
- Taking the wrong number of steps
The more indicators of impairment are present, the more likely it is that the person’s blood alcohol concentration is above the legal limit.
One-Leg Stand Test
During the one-leg stand test, an individual is asked to stand with one foot approximately six inches off the ground and count aloud by thousands until told to put their foot down. The officer times the subject for 30 seconds.
Indicators of impairment include:
- Swaying while balancing
- Using arms to balance
- Hopping to maintain balance
- Putting the foot down.
Again, the more indicators present, the more likely the person is impaired.
Defense strategies related to impaired driving charges often involve questioning the conditions under which the tests were conducted or the officer’s interpretation of the results. Highlighting these tests’ inherent limitations and potential inaccuracies can be crucial to a drunk driving defense strategy.
