Profilers say the killer of Wellington woman Mei Fan was a meticulous planner.
Police have still to catch whoever stabbed the mother of two to death in her Miramar home four months ago.
Detective Senior Sergeant John van den Heuvel told Newstalk ZB the murder was carefully executed.
"This crime was very well planned and prepared for, and it's likely that Mei's killer has discarded of items, which could be items of disguise, shortly after leaving the address."
Wellington police are following up new tips from the public, after details of the case were aired on Police 10-7 last night.
Police revealed someone broke into Mei Fen's home a month after her killing and left a bizarre note containing a biblical verse.
Detective Senior Sergeant van den Heuvel says it may have been the murderer returning to the scene of the crime.
"If it is the killer, then it's a rather paradoxical thing to do I think. To have slain a young woman, a mother of two, and then to come back and leave such a religious note.
He says the intruder left the card some time after the scene examination was complete.
"We can't discount that it is the killer returning back to the scene, to leave this card behind. And if that is the case, it's a rather unusual thing to do."