Field sobriety tests (FSTs) are a critical tool used by law enforcement officers to assess a driver’s level of impairment due to alcohol or drugs during a traffic stop. These tests are designed to detect signs of impairment and assist officers in making informed decisions about whether to proceed with a DUI (Driving Under the Influence) arrest.
The Role Of Field Sobriety Tests
Field sobriety tests serve a crucial role in identifying potentially impaired drivers on the road. They help law enforcement officers gather evidence to establish probable cause for a DUI arrest. It is essential to note that while FSTs are used for this purpose, they are not foolproof and can be challenged in court.
Three standard field sobriety tests are recognized by the National Highway Traffic Safety Administration (NHTSA) and widely used by law enforcement agencies across the United States. Each test is designed to assess specific aspects of a driver’s physical and cognitive abilities.
Horizontal Gaze Nystagmus (HGN) Test
The Horizontal Gaze Nystagmus (HGN) test is based on the observation of involuntary eye movements that occur when an individual gazes to the side. Nystagmus refers to the jerking or bouncing movement of the eye. In the HGN test, the officer uses a small object, such as a pen or flashlight, and asks the driver to follow it with their eyes while keeping their head still:
- The officer looks for three specific clues in each eye: lack of smooth eye tracking, distinct nystagmus at maximum deviation, and the onset of nystagmus prior to a 45-degree angle.
- The presence of four or more clues (two in each eye) is often indicative of impairment.
The HGN test is recognized as a reliable indicator of impairment. However, it must be conducted correctly, following strict procedures outlined by NHTSA guidelines. Any deviation from these procedures can weaken the test’s validity in court.
Walk And Turn (WAT) Test
The Walk and Turn (WAT) test assesses a driver’s ability to perform a divided attention task. During this test, the driver is instructed to take nine heel-to-toe steps along a straight line, turn around in a specific manner, and return in the same manner:
- The officer observes the driver for specific indicators of impairment, such as inability to maintain balance, stepping off the line, using arms for balance, and failure to touch heel-to-toe.
- Failing to perform the test according to the officer’s instructions can be considered a sign of impairment.
The WAT test requires precise administration and scoring to maintain its validity in court. Errors or deviations in the test’s administration can be challenged by a skilled DUI defense attorney.
One-Leg Stand (OLS) Test
The One-Leg Stand (OLS) test evaluates a driver’s balance, coordination, and ability to divide attention. During this test, the driver is asked to stand on one leg with the other foot approximately six inches off the ground while counting aloud:
- The officer looks for specific signs of impairment, such as swaying, hopping, using arms for balance, and putting the raised foot down before completing the test.
Like the other FSTs, the OLS test must be administered correctly and scored according to established procedures. Any deviations from these procedures can be challenged in court by a knowledgeable DUI defense attorney.
Challenging Field Sobriety Tests
Field sobriety tests, while widely used, are not infallible indicators of impairment. Various factors, including medical conditions, environmental conditions, and individual differences, can affect test performance. It is essential to understand that drivers have the right to refuse FSTs, and doing so does not necessarily result in automatic penalties.
Have You Been Charged?
If you or someone you know has been arrested for DUI based on field sobriety test results, it is crucial to consult with an experienced DUI lawyer in San Francisco CA. An attorney can assess the circumstances surrounding your arrest, challenge the validity of FSTs, and develop a strong defense strategy tailored to your case. Call Morales Law Firm to schedule a private consultation to find out what legal defense options you may have.