Christopher DiMeo, charged with his girlfriend in three murders and a string of jewelry store robberies in New York and Connecticut, pleaded guilty Thursday to one of the murders in a Long Island courtroom, according to media reports. He will be sentenced to life in prison without parole, the authorities reportedly said.

DiMeo, 23, whom the police have described as a heroin addict and a chronic gambler, pleaded guilty to first-degree murder and robbery as part of a plea bargain before Judge Victor M. Ort of Nassau County Court in Long Island, The New York Times reports. Judge Ort scheduled sentencing for July 28.

DiMeo admitted to killing Thomas Renison, 48, of Glen Cove, N.Y., on Dec. 21, during the robbery of the Long Island store where Renison worked, J&J Jewels in Glen Head. The police said that the robbery took place during a three-month spree in which DiMeo robbed at least four jewelry stores with the help of his girlfriend, Nicole Pearce, 23, and, in the case on Long Island, with the help of his mother, MaryAnn Taylor-Casey, 41.

Pearce and Taylor-Casey visited J&J Jewels in advance, analyzed its layout, and provided information to help DiMeo carry out the robbery, the police reportedly said. Taylor-Casey also drove the getaway car, according to court documents, and she is charged with second-degree murder and robbery.

Pearce and Taylor-Casey are awaiting trial on Long Island. As part of his plea bargain, DiMeo was promised that the murder charge against his mother would be dropped and that she would receive a 15-year prison sentence, Katie Grilli-Robles, a spokeswoman for Denis Dillon, the Nassau County district attorney told The Times.

DiMeo and Pearce were arrested Feb. 4 at an Atlantic City motel. The police said they had suspected that he would turn up there because of his penchant for gambling.

Both face additional charges in Rockland County, N.Y., and Connecticut. Among those charges, he is suspected in the slayings of Timothy Donnelly and his wife Kimberly Ann Donnelly, owners of Donnelly Jewelry in Fairfield, Conn.

JCK