Philadelphia police spent much of yesterday investigating the Christmas Eve hit-and-run accident that left a 73-year-old man dead and a 15-year-old teen as the prime suspect.

As of last night, the teen, who was too young to have a driver's license and who had taken his parents' Ford Expedition without permission, had not been charged with a crime.

"He has not been locked up, arrested, but he is still under investigation," said Sgt. Ray Evers, a police spokesman.

"Everything is still under investigation," said an officer with the department's Accident Investigation Division who declined to give his name. "Most likely he will be charged on Monday with vehicular homicide and leaving the scene of the accident."

The youth, whom police did not identify, turned himself in on Christmas and was released into the custody of his parents pending the filing of charges.

"He's very cooperative, so we don't expect him to flee," the AID officer said.

Police are still investigating whether drugs and/or alcohol were involved and whether the driver was alone in the vehicle or with others at the time of the accident.

Police said that the teen struck Bill Wrigley, 73, about 9:30 p.m. as he walked across the intersection on M Street near Erie Avenue in the city's Juniata Park neighborhood.

Wrigley, of Frankford Avenue near Luzerne Street, was taken to Temple University Hospital, where he died of his injuries. *