What Are Field Sobriety Tests?

Challenging Field Sobriety Tests in a DUI Case

Standardized Field Sobriety Tests (SFSTs) play a critical role in DUI investigations and arrests. According to the National Highway Traffic Safety Administration (NHTSA), research sponsored by the agency led to the development of these tests in 1975, with official implementation in DUI investigations beginning in 1981.

What Are Standardized Field Sobriety Tests?

During a DUI stop, police officers typically administer three NHTSA-approved Standardized Field Sobriety Tests to determine whether there is probable cause for a DUI arrest:

1. Horizontal Gaze Nystagmus (HGN)
   This eye test detects involuntary jerking or twitching of the eyes, which can occur at different angles in intoxicated individuals.

2. Walk-and-Turn Test
   The driver must walk nine heel-to-toe steps in a straight line, turn, and return the same way. This test checks balance, coordination, and the ability to follow instructions.

3. One-Leg Stand Test
   The individual must lift one leg about six inches off the ground and count aloud to 30. This test evaluates balance and divided attention.

The Importance of Proper Test Administration

For field sobriety test results to be valid, they must be administered and scored in a standardized and uniform manner. The NHTSA provides detailed training manuals and protocols for law enforcement. However, improper administration or scoring is common and can invalidate the results.

Challenging Field Sobriety Test Results

An experienced DUI defense attorney can challenge the validity of field sobriety tests by analyzing whether the arresting officer followed NHTSA guidelines. If the tests were improperly administered or interpreted, the defense may be able to:

• Suppress blood or breath test results during the pretrial phase due to lack of legal probable cause.

• Argue illegal arrest, thereby undermining the foundation of the prosecution’s case.

• Cross-examine the officer at trial to expose procedural errors and weaken their testimony.

Suppressing DUI Evidence Based on Faulty Sobriety Testing

If a police officer’s testimony relies on field sobriety test results to claim the driver was too impaired to operate a vehicle safely, any deviation from NHTSA protocol can make those results scientifically unreliable. This can lead a judge or jury to question their credibility and may result in:

• Exclusion of evidence

• Reduction or dismissal of charges

• Stronger negotiating power for plea deals