Eighty-four-year-old Jane Morgan fought for her life and, in doing so, gave police the evidence they needed to catch her suspected killer.

Yesterday, police said DNA evidence found under the fingernails of the Upper Darby woman matched that of a man who lived two floors below her in Long Lane Apartments.

William Williams, 61, was charged with murder, aggravated assault, rape, burglary, and other crimes. Police said that Williams confessed to killing Morgan after an argument, and that he "staged" her body to make the death look natural.

Investigators determined that $1,200 belonging to the victim was missing from her apartment.

Morgan, who was known for her affection for cats, was found dead in her fourth-floor apartment on Sept. 9 when she failed to answer her door after arranging a ride to a nursing home to visit a friend.

She was lying on her bed in an open nightgown with a pillow on her lap. Initially, she was thought to have died of natural causes.

The medical examiner ruled her death a homicide as a result of "asphyxiation associated with blunt-force injuries," according to court papers. She had been sexually assaulted.

Michael Chitwood, Upper Darby superintendent of police, said Williams was on authorities' "radar screen" early in the investigation. In December, Williams agreed to submit a DNA sample to Upper Darby police.

On Friday, lab results implicated him. The DNA evidence taken from Morgan and compared to that of Williams was the "slam dunk" that police needed for the arrest, Chitwood said.

At the time of the murder, Chitwood called whoever killed Morgan "an animal."

Yesterday, he changed his mind.

"Even animals don't kill for sexual gratification," Chitwood said.

Williams was arrested in 1980 for rape and served time in prison. He also was arrested in 1979 for arson and in 1976 for possession of a firearm, Chitwood said.

Williams, who is unemployed, is also charged in a 2008 theft from another elderly woman in the apartment complex, according to court documents.

Detective George Rhoades said he thought of Morgan every day since the murder as he walked by her name on the board where detectives list the victims of crime.

"Now I can take Jane's name off my board," Rhoades said. "I've been waiting nine months to do that."

Contact staff writer Mari A. Schaefer at 610-892-9149 or mschaefer@phillynews.com.