Worcester, Mass. ? The inmate accused of strangling John Geoghan in his prison cell hated homosexuals and began plotting the attack on the child-molesting former priest weeks ago, a prosecutor said Monday.

“He looked upon Father Geoghan as a prize,” Dist. Atty. John J. Conte said. “No question he had been planning it for well over a month.”

Joseph L. Druce, who is serving a life term for killing a gay man 15 years ago, cut apart a book to make a perfect tool for jamming the door of Geoghan’s cell and spent time stretching the socks used in the strangling, Conte said.

Druce “has a long-standing phobia, it appears, toward homosexuals of any kind. … He is filled with long-standing hate,” Conte said as he provided new details into the death of the central figure in the Roman Catholic Church sex scandal.

Druce and Geoghan had just finished lunch in their cells at the maximum security Souza-Baranowski Correctional Center in Shirley. They were let out to return their trays when Druce followed Geoghan into his cell about 11:52 a.m. Saturday, before the doors were locked again, Conte said.

In the upper track of the cell door, Druce jammed a book he had doctored to fit the slot, then put nail clippers and a tooth brush in the door’s lower track to prevent guards from opening the door. He had precut the book to fit into the track, Conte said.

He tied Geoghan’s hands behind his back with a T-shirt, then used the stretched-out socks, a pillow case and one of Geoghan’s shoes to strangle him, Conte said. Druce did not use a razor he had with him, but may have intended to castrate the former priest, Conte said.

Once he was alerted to the attack by an inmate, the guard on duty tried to get inside, but found the door was jammed. He called for help. By the time a nurse arrived to treat Geoghan, seven or eight minutes had passed, Conte said.

Geoghan, 68, was taken to Leominster Hospital, where he was pronounced dead at 1:17 p.m. An autopsy Monday showed that Geoghan died from strangulation and blunt chest trauma. He also had broken ribs and a punctured lung, Conte said.

Conte has said Druce will be charged with murder once a grand jury is convened in September. Druce, who remains in isolation in the prison, has been cooperative with investigators, Conte said.