The Supreme Court's justices put themselves in the driver's seat Tuesday, hearing arguments in two cases involving vehicle searches, but it was unclear what routes the justices will take to resolve the cases.

One case involved Pennsylvania state troopers' stop of a rental car driven by a man who wasn't on the rental agreement. The second involved a policeman's search for a stolen motorcycle in Virginia.

"One of the things that I think is very important in these types of cases is the ability to give clear guidance not only to the courts but to the police," Chief Justice Roberts said. Justice Stephen Breyer, when trying to describe a resolution to the case, said he was "looking for something simple."

The first case involves Terrence Byrd, who was driving his fiancee's rental car on a Pennsylvania highway when a state trooper pulled him over for an alleged minor traffic violation. He acted nervous during the stop and told troopers he had a marijuana cigarette in the car, and officers decided to search the car.

Because the rental agreement didn't authorize Byrd to drive the gray Ford Fusion, troopers told him they didn't need his consent for the search. And when troopers opened the trunk, they found body armor and about 2,500 little bags of heroin. Byrd later acknowledged he planned to sell the drugs for roughly $7,000, and a court sentenced him to 10 years in prison.

Byrd's attorneys argue his case has potential consequences for the 115 million car rentals that take place annually in the United States. They say that if the government wins, police will have an incentive to pull over a rental car driver who commits a traffic violation because police will know they can search the car if the driver isn't on the rental agreement.