NEW YORK (AP) — A man has been charged with cutting off his pregnant girlfriend’s head on a New York City rooftop in 1989.

Philip Ward pleaded not guilty Monday to murdering Veronica Bowen.

Ward already is in prison for killing the woman who became his girlfriend after Bowen’s death.

Although he entered a not guilty plea, prosecutors said he recently confessed to a crime in which he’d long been under suspicion. His lawyer, Franklin Rothman, said the 45-year-old Ward was helping authorities, spurred by a desire to build a better relationship with his and Bowen’s two children.

“I killed Veronica Bowen,” he told investigators last month at the upstate New York prison where he’s serving 20 years to life for killing his subsequent girlfriend, according to prosecutors’ court papers.

Bowen was 21 when she disappeared in February 1989. She and Ward had met as teenagers at a group foster home and developed a relationship marred by domestic violence, the Manhattan district attorney’s office said. She had recently moved out of the upper Manhattan apartment they shared, prosecutors said.

After finding out she was carrying another man’s child, Ward lured her to the apartment building’s roof overlooking the Hudson River, beat her with a pipe, stabbed her with a dagger and ultimately cut off her head with a kitchen knife, Manhattan Assistant District Attorney Elizabeth Lederer told a judge.

He bagged Bowen’s head and hid it in a hole he dug in a nearby area, Lederer said. Her body was left on the roof, where it was discovered 15 days later. Her head has never been found, though Rothman said Ward had recently given investigators information to help them look for it.

After Bowen’s death, Ward moved on to another relationship that ended in violence. He admitted in 1994 to shooting and killing another girlfriend, caterer Sheila Jackson, in front of her 11-year-old daughter at the home they all shared in a New York suburb.

While serving his sentence for killing Jackson, Ward has gotten a high-school degree and gotten training in masonry and metal assembly, among other things, according to state Department of Corrections and Community Supervision spokeswoman Linda Foglia.

He also has been trying to forge ties to his children, recently meeting with them under authorities’ watch “to air out some things,” his lawyer said.

“He’s very reserved, very calm,” Rothman said. “His motivation, at this point, appears to be to have some type of relationship with his children.”

Copyright 2012 The Associated Press.