Trial Tactics
Standardized Field Sobriety Tests (SFST): NHTSA Protocols & Inherent Inaccuracies
Legal Counsel Review: Senior DUI Trial Attorney & Forensic Specialist•Published: September 2, 2026•Statutory Jurisdiction: State & Federal Courts
Developed by the National Highway Traffic Safety Administration (NHTSA), Standardized Field Sobriety Tests (SFSTs) are divided attention physical exercises designed to establish probable cause for DUI arrests.
1. The Three NHTSA-Validated Tests
- Horizontal Gaze Nystagmus (HGN): Measures involuntary jerking of the eyeball. Natural medical conditions (inner ear infections, caffeine, astigmatism) produce false positives.
- Walk-and-Turn (WAT): An 8-clue divided attention test. Requires a dry, hard, flat, non-slippery surface and proper footwear.
- One-Leg Stand (OLS): A 4-clue balance evaluation. Individuals over 65 years of age or more than 50 pounds overweight are excused under NHTSA guidelines.
| Test Type | Clues Required for Arrest | NHTSA Statistical Reliability | Common Defense Defenses |
|---|---|---|---|
| HGN | 4 of 6 Clues | 77% Accuracy | Medical nystagmus, strobe light interference, improper stimulus speed |
| Walk-and-Turn | 2 of 8 Clues | 68% Accuracy | Uneven asphalt, wind, passing highway traffic, footwear issues |
| One-Leg Stand | 2 of 4 Clues | 65% Accuracy | Orthopedic injuries, inner ear imbalance, nervousness |
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Authored & Verified by Duiattorneysonline Senior Trial Counsel
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