DUI Investigations: Field Sobriety Tests
If you’ve been pulled over on suspicion of DUI in California, chances are you were asked to step out of the vehicle and perform a series of physical tasks. These are called Standardized Field Sobriety Tests (SFSTs)—and they play a central role in how law enforcement officers assess impairment.
As a California defense attorney with experience in DUI cases, it is important for clients to understand what these tests are, how they’re supposed to work, and how they can be challenged in court.
What Are Standardized Field Sobriety Tests?
The Standardized Field Sobriety Tests are a set of three physical and cognitive assessments developed by the National Highway Traffic Safety Administration (NHTSA) to help officers determine if a driver is under the influence of alcohol:
Horizontal Gaze Nystagmus (HGN)
This test checks for involuntary jerking of the eyes as they follow a moving object (usually a pen or flashlight). Officers look for three specific clues in each eye, such as lack of smooth pursuit.Walk-and-Turn (WAT)
You’re asked to take nine heel-to-toe steps in a straight line, turn, and take nine steps back. Officers are watching for balance issues, improper turns, or failure to follow directions.One-Leg Stand (OLS)
You must stand on one leg while counting out loud for 30 seconds. The officer looks for swaying, hopping, putting your foot down, or using your arms for balance.
These tests are considered "standardized" because they are only valid when performed exactly according to NHTSA guidelines.
The Problem with SFSTs
There are several reasons why SFSTs can be unreliable indicators of intoxication:
Subjective Interpretation: Officers make judgment calls based on what they observe. Two different officers could interpret the same performance in completely different ways.
Environmental Factors: Uneven pavement, weather, lighting, or distractions from traffic can all impact test performance.
Physical or Medical Conditions: Age, weight, injuries, neurological issues, or even anxiety can affect balance and coordination—leading to false indicators of impairment.
Improper Administration: If an officer deviates even slightly from the standard instructions or scoring criteria, the test results may be invalid.
Are SFSTs Mandatory in California?
No. In California, you are not legally required to perform field sobriety tests. Politely declining these tests cannot be used against you in court the same way refusing a chemical test (like a breath or blood test) sometimes can. However, many drivers don't know this and feel pressured to comply during a traffic stop.
How a DUI Defense Attorney Can Help
Examine bodycam or dashcam footage for improper administration or environmental challenges.
Consult medical experts when a client’s health may have affected test performance.
Remember, poor performance on a field sobriety test doesn’t automatically mean you were impaired. These tests are tools—not verdicts—and they’re often far less accurate than prosecutors would like you to believe.
Facing a DUI Charge? Let’s Talk.
If you were arrested after performing field sobriety tests in California, don’t assume the evidence against you is airtight. Contact Davis W. Hewitt for a free consultation.
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