People v. Walker
199 Colo. 475, 610 P.2d 496, 1980 Colo. LEXIS 621 (1980)
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Rule of Law:
To admit radar speed evidence that was calibrated using a tuning fork, the prosecution must establish a sufficient evidentiary foundation by showing either that two tuning forks were used or that the single tuning fork used was certified for accuracy within one year of the test.
Facts:
- On June 15, 1978, Officer Cox observed Raymond L. Walker's vehicle traveling at what he believed was a rate in excess of the 35 mph posted speed limit.
- Officer Cox's 'Speedgun No. 6' radar unit indicated that Walker's vehicle was traveling at 66 mph.
- To test the radar unit's accuracy, Officer Cox used a single tuning fork designed to produce a 50 mph reading on a properly functioning device.
- He performed this test both before and after issuing a citation to Walker.
- Officer Cox testified that he had no knowledge as to whether the tuning fork itself was properly calibrated.
- No other tests were performed to verify the accuracy of the radar unit.
Procedural Posture:
- Raymond L. Walker was convicted of speeding in the Aurora Municipal Court, a court of first instance.
- Walker appealed his conviction to the Adams County District Court, an intermediate appellate court.
- The District Court reversed the conviction, holding that the prosecution presented insufficient evidence of the radar device's accuracy.
- The prosecution (the People) petitioned for and was granted certiorari by the Colorado Supreme Court, the state's highest court, to review the district court's judgment.
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Issue:
Does the use of a single, uncalibrated tuning fork provide a legally sufficient foundation to establish the accuracy of a radar device's speed reading for evidentiary purposes?
Opinions:
Majority - Justice Erickson
No. The use of a single uncalibrated tuning fork provides a legally insufficient foundation to support a reading taken from a radar device. While courts can take judicial notice of the scientific principles behind radar, the prosecution must still prove that the specific device used was accurate at the time of the alleged offense. A test's value depends entirely on the accuracy of the measuring device used to conduct it. A single, uncalibrated tuning fork cannot provide a reasonable assurance of the radar unit's accuracy because the fork itself may be inaccurate, potentially masking an error in the radar unit and making both appear correct. Therefore, to ensure reliability, the prosecution must show either that two separate tuning forks were used or that the single tuning fork had been certified as accurate within the previous year.
Analysis:
This decision establishes a specific, heightened evidentiary standard for the admission of radar evidence in traffic cases. It moves beyond a general reliability assessment and provides a clear, bright-line rule for law enforcement and prosecutors to follow when using tuning fork calibration methods. By requiring either dual-fork testing or certification, the court aims to prevent wrongful convictions based on potentially faulty equipment, thereby strengthening the foundational requirements for scientific evidence. This ruling gives defense attorneys a concrete basis for challenging the admissibility of radar readings if these specific calibration procedures are not documented and followed.
