Police criminal profilers have been called in to help with the investigation into the death of Auckland grandmother Cunxiu Tian in West Auckland.
The 69-year-old Chinese woman died a violent death and was struck multiple times around the face and neck, police say.
A post-mortem examination late Saturday concluded she was the victim of a prolonged attack. Police say the killer would likely have been covered in blood when he left the Glenvil Lane property.
Canterbury University criminologist Greg Newbold today said the use of criminal profilers suggested to him the murder was a "random act" and not family or Chinese community-related.
Professor Newbold, who has inside knowledge of the New Zealand criminal underworld, said he believed the killer acted alone.
"Sometimes they operate in pairs, but often with a brutal attack like this you would expect it to be a solo assault. You wouldn't expect two people to go mad on an old woman," he said.
"You'd expect it to be the work of one person ... [another] person may be an accessory before the fact but I think the principal perpetrator did it alone."
He believed police should be looking for a person who was young, aged between 15 and 22, and male.
"There's often an element of racism in these kind of crime, but I think in this case the woman was targeted because she was old, frail and alone."
In his opinion, the killer was also likely to be unemployed and have a criminal record.
"The police will have their eyes wide open and won't be blinding themselves to other possibilities," added Professor Newbold.
"Sometimes the perpetrators of these crimes are women ... they are a minority, it's not common, but it happens."
Detective Senior Sergeant Roger Small today said the attacker would have had a lot of blood on them, and appealed for help from anyone who may have seen something last Friday.
"We are appealing to the public to consider whether a family member, friend or flatmate has come home on Friday, anytime after 9am, and has blood on their body, their clothes or their shoes," he said.
"They may have been acting strangely and have washed themselves or their clothing immediately, or have thrown their clothes or shoes out."
"If you've noticed any stains on clothing of someone you know that may resemble blood, we need to hear from you," Mr Small said.
"We'd also like to hear from anyone who has seen discarded clothing or shoes in public areas and parks that look like they've got blood on them, particularly in West Auckland."
The police specialist profiling unit and 10 additional investigation staff returned to the property yesterday to examine and assess the crime scene.
So far, detectives have visited more than 125 homes in the Te Atatu area and spoken with more than 300 residents.
Investigators were continuing to gather and review CCTV footage from the wider Te Atatu area.
"Ms Tian was a much-loved family member and we are doing everything we can to identify and locate the person or persons responsible for this appalling criminal act," Mr Small said.
Anyone who witnessed suspicious behaviour or had an attempted break-in that they didn't report was asked to contact police on 0800 77 22 71.