BOSTON (AP) — The trial of a 30-year-old man accused of killing a popular Boston grandmother is underway.

Timothy Kostka (KOSS'-kuhz), of Boston, previously pleaded not guilty to first-degree murder in the fatal stabbing of 67-year-old Barbara Coyne in 2012.

Richard Coyne testified in Superior Court Thursday that his mother said she'd been stabbed by someone in a white shirt and a hat.

Prosecutors described Kostka as a "heroin addict looking for a score" who beat and slashed Coyne's throat in her bedroom before taking lottery tickets and washing her blood off in the kitchen.

Kostka's attorney says a security camera at a nearby store showed Kostka cashing lottery tickets in a spotless tank top and sneakers. He said the killer would have been covered in blood.

Testimony is scheduled to resume Friday.