Constitutional Law
Fourth Amendment Search & Seizure: Challenging Unlawful Traffic Stops and Checkpoints
Legal Counsel Review: Senior DUI Trial Attorney & Forensic Specialist•Published: September 2, 2026•Statutory Jurisdiction: State & Federal Courts
Under the Fourth Amendment to the United States Constitution, police officers must possess specific, articulable facts establishing reasonable suspicion of a vehicle code infraction or criminal conduct before executing a traffic stop.
1. Grounds for a Penal Code § 1538.5 Motion to Suppress
- Pretextual Stops Without Probable Cause: Weaving within a single lane without crossing boundary lines does not constitute reasonable suspicion under established California case law (People v. Carmona).
- Unconstitutional DUI Sobriety Checkpoints: Checkpoints that fail to comply with the Ingersoll criteria—including neutral vehicle selection formulas, advance public advertising, and supervisor oversight—are legally invalid.
- Unlawful Detention Extension: Extending a traffic stop beyond the time necessary to issue a mechanical citation without independent DUI suspicion violates Rodriguez v. United States.
| Constitutional Violation | Defense Remedy | Case Outcome |
|---|---|---|
| Lack of Reasonable Suspicion for Stop | Penal Code § 1538.5 Suppression Motion | All BAC tests and officer observations suppressed; Case Dismissed |
| Non-Compliant Checkpoint Location | Motion to Dismiss under Ingersoll | Entire checkpoint arrest sequence ruled unconstitutional |
⚖️
Authored & Verified by Duiattorneysonline Senior Trial Counsel
Our legal research desk analyzes Title 17 forensic compliance standards, NHTSA standardized field sobriety test administration manuals, DMV administrative per se hearing precedents, and Fourth Amendment search and seizure suppression strategies.