The Basic Speed Law & Motions to Suppress Based Upon a "Speed Law" based Traffic Stop
Many arrests start with a traffic stop and a large number of traffic stops are based upon a violation of the basic speed law. Even if you were exceeding the "speed limit", nuances in the basic speed law may (in some cases) permit you to suppress the stop and search of your car.
In the context of making a motion to suppress a car stop based on allegations that the speed limit was too low and the person did not violate the basic speed law, several factors and legal precedents come into play:
Basic Speed Law and Speed Limits
According to California's Vehicle Code § 22351, driving in excess of posted speed limits is prima facie unlawful unless the defendant can show with competent evidence that such speed did not violate the basic speed law given the existing conditions at the time (Vehicle Code § 22351) The basic speed law itself states that no person should drive at a speed greater than is reasonable or prudent under the circumstances, regardless of the posted speed (People v. Difiore, 197 Cal.App.3d Supp. 26 (1987)); People v. Goulet, 13 Cal.App.4th Supp. 1 (1992); People v. Huffman, 88 Cal.App.4th Supp. 1 (2000)
Speed Traps and Legal Challenges
The legality of the posted speed limit can be challenged if it is deemed a "speed trap." For a speed enforcement to be considered a speed trap, the speed limit must not be justified by a current engineering and traffic survey (People v. Difiore, 197 Cal.App.3d Supp. 26 (1987); (People v. Miller, 90 Cal.App.3d Supp. 35 (1979); (People v. Conzelman, 33 Cal.App.4th Supp. 6 (1994))[6]. If a speed limit is found to be unsupported by such a survey, evidence of exceeding that speed limit may be deemed inadmissible.
Suppressing Evidence Based on Speed Traps
The California Vehicle Code and case law suggest that evidence from a speed trap can be suppressed (People v. Huffman, 88 Cal.App.4th Supp. 1 (2000); People v. Hardacre, 116 Cal.App.4th 1292 (2004). This was illustrated in cases where defendants successfully challenged the admissibility of speed evidence on the grounds that the speed limits were not justified by a current traffic survey (People v. Difiore, 197 Cal.App.3d Supp. 26 (1987); (People v. Conzelman, 33 Cal.App.4th Supp. 6 (1994).
Reasonable Suspicion and Speed Estimation
Even if a speed limit is later found to be unsupported by a traffic survey (and thus a speed trap), an officer’s reasonable suspicion at the time of the stop, based on their observation or speed estimation, can still be valid. This was highlighted where courts have held that initial stops did not violate constitutional protections against unreasonable searches and seizures, as the officer had reasonable suspicion at the time of the stop (People v. Hardacre, 116 Cal.App.4th 1292 (2004)
Based on these points, one could argue that challenging the validity of a speed limit as being too low could be a valid defense if it can be shown that the speed limit qualifies as a speed trap due to lack of a current and valid traffic survey. However, the success of a motion to suppress based on such an argument would also depend on whether the officer had reasonable suspicion based on other observations at the time of the stop.
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