Police officers who initiate a traffic stop because they have reasonable suspicion that the driver is impaired have a few options to determine whether that’s the case. One method of impairment detection that is frequently employed involves conducting field sobriety tests.
A field sobriety test requires a driver to engage specific actions that might not be straightforward if the person is impaired. It’s important to note that these tests are voluntary, but officers might state their request in a way that makes it seem like they’re compulsory.
Standardized versus non-standardized field sobriety tests
Field sobriety tests can be categorized into two main types: standardized and non-standardized. Non-standardized tests have no uniform application or grading system and can vary widely from one jurisdiction to another. Examples include asking a driver to recite the alphabet or to touch their nose with their finger.
Standardized field sobriety tests (SFSTs) are three tests endorsed by the National Highway Traffic Safety Administration with established guidelines and scoring systems. These include the Horizontal Gaze Nystagmus, Walk-and-Turn, and One-Leg Stand tests.
Components of the SFST
The SFST consists of three specific tests designed to evaluate a driver’s balance, attention level and eye movements, which can be indicators of alcohol or drug impairment.
The Horizontal Gaze Nystagmus test checks for involuntary jerking of the eyes as they move side to side, which can become exaggerated by alcohol consumption.
The Walk-and-Turn test assesses the driver’s ability to follow instructions, maintain balance and complete tasks simultaneously.
The One-Leg Stand test measures balance and concentration as the driver is asked to stand with one foot approximately six inches off the ground for a 30-second period.
The role of field sobriety tests in a drunk driving case
Field sobriety tests may play a critical role in drunk driving cases. They’re often the primary evidence the prosecution uses to establish that a driver was impaired at the stop. Performance on these tests can significantly influence the outcome of a case, including the decision to arrest and charge a driver with impaired driving.
It’s important to note that while SFST results can be compelling evidence, they aren’t infallible. Various factors, such as medical conditions, disabilities and even nervousness, can affect a person’s performance on these tests. These concerns may be used as part of a defense strategy, so defendants who have been subjected to such testing should work with a legal representative who can help them determine how best to proceed.