In Commonwealth v. Whitmyer, 542 Pa. 545, 668 A.2d 1113 (Pa. 1995), the officer's observations were that the defendant changed lanes and drove at an unsafe speed, in excess of the speed limit. Id. at 1114.
While the Whitmyer Court discusses Fourth Amendment jurisprudence, our reading of the opinion is that the court's conclusion rested on the interpretation and application of state statutes, particularly a provision that required an estimate of speed to be based on following the vehicle for at least three-tenths of a mile. See id. at 1117.
The officer had followed the defendant for two-tenths of a mile, not three-tenths as required by the statute, and there was no other evidence of a motor vehicle violation constituting probable cause for a stop. Id.
75 Pa. Cons. Stat. Section 3368(a)(2002) provides: "Speedometers authorized.-- The rate of speed of any vehicle may be timed on any highway by a police officer using a motor vehicle equipped with a speedometer. In ascertaining the speed of a vehicle by the use of a speedometer, the speed shall be timed for a distance of not less than three-tenths of a mile." Whitmyer, 668 A.2d at 1114 n.5.