A post-mortem examination has confirmed father of two Michael Mulholland was seriously assaulted before his death in Taita, Lower Hutt, last Thursday.
The 52-year-old was found unconscious in a driveway near his Farmer Crescent home. Friends attempted CPR, which was continued by emergency services, but he died at the scene.
Operation Field inquiry head Detective Inspector Darrin Thomson said the post mortem confirmed Michael had suffered serious injuries before his death.
He said police were following several positive lines of inquiry in relation to the homicide investigation.
"Police believe a number of people visited Michael's home at 93 Farmer Crescent on Thursday 20 September 2012, and would like to speak with anyone who had contact with him at any time during that day as they may hold key pieces of information about what happened to Michael at about 10pm that evening."