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Lesson 5.
Trial Procedures



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§5.05 Engineering and Traffic Survey

When the officer’s means of determining the defendant’s speed included the use of radar or another electronic device, the prosecution must produce a current engineering and traffic survey to meet its burden of establishing a prima facie case that there was no speed trap. Without the survey, the arresting officer is incompetent to testify about the speed of the defendant’s vehicle even if the officer’s testimony is confined to his or her visual determination of speed. [See VC §40804(a); People v Conzelman (1994) 33 CA4th Supp 6, 8–9.] If the prosecution fails to justify the posted speed limit with such a survey, you must exclude all evidence of the defendant’s speed. [People v Studley (1996) 44 CA4th Supp 1, 3.]

When an engineering and traffic survey is introduced into evidence, you must determine whether the survey:

  • Complies with methods determined by the Department of Transportation;
  • Considered prevailing speeds, accident records, and conditions not readily apparent to drivers (it also could have considered residential density and the safety of pedestrians and bicyclists) [VC §627; People v Goulet (1992) 13 CA4th Supp 1, 9–10]; and
  • Justifies the speed limit—i.e., shows that the speed limit is just and based on sufficient lawful reason [13 CA4th Supp at 9]. The speed limit should be set at the nearest 5-mph increment to the 85th percentile critical speed unless the survey lists other factors justifying a reduction [Cal Manual on Uniform Traffic Control Devices (MUTCD) §2B.13].

Example Click

If you determine that the speed limit is not justified by the facts stated in the survey, you must dismiss the speeding charge. If you determine that the speed limit is justified by the survey, then you must decide whether guilt is proved beyond a reasonable doubt. [13 CA4th Supp at 13.]

An engineering survey is not required:

  • For a local street or road [VC §40802(b)(1)],
  • For a posted school zone while children are present [VC §40802(b)(2)],
  • For a senior center zone [VC §22352(a)(2)(C)],
  • For highways with statutory maximum speed limits [see, e.g., VC §22349(a)­­–(b) (exceeding 65 mph or 55 mph)], or
  • When the officer is pacing with a speedometer or not using radar or lidar [see People v Goulet, supra, 13 CA4th at 3].


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