A 33-year-old woman has been arrested in the Greater Shankill area of Belfast by detectives from Serious Crime Branch investigating the murder of 26-year-old David Clarke in north Belfast in 2001.
Mr Clarke was found battered to death at his north Belfast flat in June 2001.
Police believe Mr Clarke, who was described as vulnerable and inoffensive, had been bullied in the weeks leading up to his death.
It is understood a number of people, including a woman, were in his property at Forthriver Road on the night he was killed.
Police said the suspect was detained in the Shankill area on Tuesday morning.
Detectives have made a number of arrests since the murder investigation was reopened last month following fresh information.
Detective Chief Inspector Alan Dickson said: “I would continue to ask anyone with information to do the right thing and come forward with anything they know.”
Anyone with information is asked to contact police on 10