3 Young Sisters Held in Death of Neighbor : Crime: They had boasted to friends about the killing, detective says. The girls deny murder charge.

Three Northridge teen-age sisters were charged Friday with beating and stabbing to death a 62-year-old neighbor, a librarian who befriended them, took them to school and cared for their cats, police said.

“It is hard to explain,” said the detective investigating the Nov. 21 slaying of Meta Frances Murphy. “At the time of the killing, these girls were only 12-, 15- and 16-years-old.”

They were caught because they boasted to friends about the killing, he said.

Each of the girls appeared in Sylmar Juvenile Court on Friday and denied a charge of murder--the legal equivalent of pleading not guilty in a higher court. All three were being held by juvenile authorities pending a detention hearing set for June 18.

Murphy, a librarian at the Panorama City branch of the Los Angeles City Library, lived alone in the neatly kept condominium complex in the 18500 block of Mayall Street.

Her body was discovered Nov. 21 by police who were called after co-workers became concerned when she did not report to work. She was found beaten and stabbed 11 times in the back, her body covered with five neatly placed coats in a closet. Police said there was no sign that her townhouse had been broken into.

Detective Mitch Robins said the three girls accused of killing Murphy had lived next door with their parents for the past three years. The two older girls attend a school in San Fernando and the younger girl attends an elementary school in Northridge.

Robins said Murphy and the three girls had a friendly relationship before the killing, with the librarian taking them to school on some days and sharing her love of cats with the girls. Murphy and the girls had cats and took turns caring for each others’ pets, the detective said.

“The motive is still under investigation,” Robins said. “We are not really sure why this occurred. As neighbors, they were friendly.”

Robins said it was possible the girls were burglarizing Murphy’s home when she surprised them and they killed her, but he added that valuable property was left in the condo.

“We have not been able to determine if anything was taken,” he said.

Robins said a break in the case came when two teen-agers came to police this week and said the three girls had told them about the killing about a week after it happened.

“The three juveniles boasted to the two friends about the killing,” Robins said. “They were telling them how they did it. The two friends decided it was time to come forward and tell us.”

Police said the two friends’ account was corroborated by physical evidence, which detectives did not reveal.

Authorities declined to disclose whether one of the girls is suspected of stabbing Murphy or whether all three took part.

Deputy Dist. Atty. William Ryder said he will decide Monday whether to ask that the oldest girl, now 17, stand trial as an adult. Under California law, a suspect who was 16 or older at the time of a crime can be tried as an adult if a judge approves.

The sprawling Peppertree condominium complex at Mayall Street and Reseda Boulevard where Murphy and the girls lived is inhabited by a mix of families, professionals and students who attend nearby Cal State Northridge.

Residents of the two-story complex surrounded by trees and heavy landscaping were surprised last November when Murphy was found dead. They were shocked again Friday when they learned that authorities believe three young residents were responsible.

“I’m surprised,” said a man who lives near the girls’ home. “I used to think it was a nice neighborhood. It’s not like downtown L.A. here.”

The man said he did not know the girls or their parents, but that their townhouse had frequent teen-age visitors.