Law & Order S12E05 - Possession

Investigating the murder of a woman in a rent-controlled apartment, Green and Briscoe initially turn their attention to janitor Roberto Ramos, who had been given a cash gift of $5,000 by the deceased but claimed he didn't remember her when questioned. But it isn't long before the detectives discover that she was engaged in a long-running battle with her landlord and had been blocking the potentially lucrative sale of the building.