A 63-year-old Hillcrest Heights woman was fatally injured Saturday when her car was struck by a patrol car driven by a Prince George's County policeman responding to a call for assistance from another officer, police officials said yesterday.

Police identified the victim as Bessie Mae Tucker of 2604 Colebrooke Dr. They said she was pronounced dead shortly after the 4 p.m. accident, which occurred in the 2300 block of Iverson Street in Hillcrest Heights.

Witnesses said Tucker's car was struck broadside by the patrol car and crashed into a tree as she pulled out of the Hillcrest Heights Shopping Center parking lot. A passenger in Tucker's car, identified as her 11-year-old granddaughter, Lorena Daniels, suffered possible internal injuries in the crash and was listed in fair condition yesterday at D.C. General Hospital.

Investigators said yesterday that Tucker had failed to yield the right of way leaving the parking lot and drove into the path of the police car. They said the officer, identified as Jerry F. Forsythe of the Oxon Hill police substation, was driving at about 25 to 30 miles an hour and was unable to brake in time to avoid a collision.

Officials said Forsythe, 24, was going to the aid of a fellow officer who had radioed moments earlier for help in chasing a theft suspect near the shopping center. Forsythe was not using the emergency lights and siren on his cruiser at the time, but a police spokeswoman said yesterday that he was conforming to normal department rules.

Even though it was a priority call, "he was only a block away, and other cars were closer to the scene . . . . He was not expediting," the spokeswoman said. Under county police regulations, she said, an officer who has no need to hurry to a scene or to maneuver through traffic does not have to employ his siren or flashing dome lights.

"There were no rules broken as far as the police department is concerned," she said.

Forsythe suffered head, back and facial injuries in the accident and was treated at Southern Maryland Hospital Center in Clinton and released.