A Medford man accused of stabbing his live-in girlfriend to death pleaded not guilty at his arraignment Tuesday afternoon.

Robert Heise, 42, was in Central Islip court to face a second-degree murder charge. Police say Heise repeatedly stabbed Donna Ruisi, 50, during an argument Monday night at 18 Pine Grove Ave. where they were renting a room.

Police described the home as a “boarding house” which are illegal in the Town of Brookhaven. A town spokesman says there's a history of code violations at the house, including a lack of permits required to rent the space.

Court records show the homeowner, Scott Carnel, pleaded guilty last year to not having a valid rental registration for the property. He told News 12: “I don't care what the town says…The town don't know what I got.”

Ruisi’s family was in the courtroom. They say she was a loving grandmother and mother who worked for years as a home health aide.

Heise has no prior convictions, but was arrested earlier this month and charged with assault for an incident that prosecutors said did not involve Ruisi.