Rodney Scarman, 52, was found dead inside the electrical cupboard of a housing commission block on Walker Street about 4.30am on Boxing Day 2011.

Mr Scarman, a disability pensioner, lived in the housing commission block and was last seen a few hours earlier.

Police inquiries suggest the incident was drug-related and the people involved may live nearby, Redfern Local Area Commander Superintendent Luke Freudenstein said.

Police have asked anyone with information to come forward.

"Mr Scarman was a well known resident of a busy unit complex. There is no doubt that there are people who know what happened to him and I am pleading with those people to come forward and assist us," Superintendent Freudenstein said.

"Today is the third anniversary of his death and we want to be able to put closure to this and allow his family to start the process of moving on."

Mr Scarman's sister Robyn Turner said Christmas has not been the same since the death of her brother.

"It's been three years since we lost Rodney and it's fair to say that Christmas isn't the same for us anymore," Ms Turner said.

"Losing him was hard enough but not having any answers has made it even worse for our family.

"I am pleading with people to look into their conscience and have the courage to come forward and speak with the police, no matter how small they think the information is.

"Please think, if it was your family member you would want someone to speak up."

Police have asked anyone with information to contact Crime Stoppers on 1800 333 000 or visit the Crime Stoppers online reporting page.