The Suffolk County Grand Jury yesterday returned an indictment charging a South Boston man with first-degree murder for the beating death of 65-year-old Barbara Tagen in her Andrew Square apartment, Suffolk County District Attorney Daniel F. Conley said.

ADAM CASSINO (DOB 5/9/86), who lived across the street from Tagen, is expected to face arraignment on that charge on Dec. 1 in the Magistrate’s Session of Suffolk Superior Court. He has been held without bail since his district court arraignment on Sept. 22.

Tagen’s loved ones last heard from her on Aug. 23. The next day, a judge committed Cassino to Massachusetts Alcohol and Substance Abuse Clinic at Bridgewater State Hospital at the request of his mother. On Aug. 27, Tagen’s body was found in her Dorchester Street residence. She appeared to have been dead for several days after suffering severe head trauma.

When Cassino arrived at the treatment center, Conley’s office says, his sneakers had bloodstains on them that were later matched by DNA testing to the victim. Boston Police homicide detectives also recovered a blunt item, with traces of blood that matched the victim’s DNA, from an apartment where Cassino stayed on Aug. 22 and 23. This item was consistent with Tagen’s injuries and other evidence at the scene.

The indictment capped a two-month grand jury investigation. Evidence indicated that Cassino had previous conflicts with Tagen over allegations that he stole prescription drugs from her.

Katherine Moran is the DA’s assigned victim-witness advocate. Cassino is represented by attorney Lorenzo Perez.