Under Pennsylvania law, for a police officer pull over a car, he or she must have a reasonable and articulable ground to suspect that the car's occupants have committed or are committing a crime. This standard is found in the state code and is based on the Fourth Amendment's prohibition of unreasonable searches and seizures.
One common reason police officers give for pulling over a vehicle is that the vehicle appeared to have improper identification on it, such as expired tabs or license plates that do not seem to match with the vehicle to which they are attached. That is the justification officers in West Newton, Pennsylvania, are giving for a traffic stop early in the morning of Feb. 1 that led to them arresting two men on suspicion of possession of heroin.
The men were driving in a Ford Explorer around 1:10 a.m. when a police officer pulled them over. The officer later claimed in an affidavit of probable cause that he discovered 80 small baggies "in plain view" within the car that he believed contained heroin. Based on that suspicion, the officer conducted a search of the car and found five more bags that may have contained heroin, as well as three syringes and two spoons.
The officer justified his pulling over the car by saying the license plates on the car were registered to a Jeep instead of the Explorer.
The suspects, a 19-year-old Pittsburgh man and a 26-year-old West Newton man, were arrested and charged with possession of a controlled substance, possession with intent to deliver, possession of drug paraphernalia, conspiracy and proving false identification to police. The court set bond at $750,000. The men were being held at Westmoreland County Prison as of Feb. 2.
Source: Pittsburgh Tribune-Review, "2 charged in West Newton heroin case," Paul Peirce, Feb. 2, 2012