A motor vehicle stop enacted without the proper level of suspicion violates the United States Constitution, and the Pennsylvania Constitution. Vehicle searches and stops in criminal cases may trigger violations of an accused's rights under the US constitution. Vehicle searches and stops generally reuire that the police possess probable cause. Generally, in order to effectuate a motor vehicle stop a police officer must have reasonable suspicion that a violation of Title 75 is or has occurred. 75 Pa.C.S. § 6308(b). Suppression motions However, where an officer merely has reasonable suspicion that a violation of the motor vehicle code has occurred, and more cannot be gained by investigation during a seizure, then it cannot be a valid stop. The Pennsylvania Supreme Court in a case named Chase explained that before a police officer may stop a single vehicle to determine whether or not the vehicle is being operated in compliance with the Motor Vehicle Code, he must have probable cause based on specific facts which indicate to him either the vehicle or the driver are in violation of the vehicle code.
The Pennsylvania Supreme Court found that an observation of "erratic lane changes" does not fit within the "ambit of prohibited vehicle operations as defined in [75 Pa.C.S.] section 3361." In Whitmyer the Supreme Court reviewed a vehicle stop and stated: We note that this is not a case where further investigation would lead to a discovery of a violation of the Vehicle Code. DUI Basics If the trooper was unable to clock Appellee for three-tenths of a mile or observe the conditions that would warrant a citation for driving at an unsafe speed, there is no further evidence that could be obtained from a subsequent stop and investigation.
In order for the police to stop a car they must have Probable cause showing that it was necessary to effectuate a stop a vehicle.