Lois Tolley killing suspects narrowed down to 12

Almost a year on from the brutal killing of Lois Tolley in her Upper Hutt home, a dozen people remain persons of interest to police.

They include those who were allegedly directly involved in her death, helped plan the attack or helped the killers afterwards.

Detective Senior Sergeant Glenn Barnett, the officer in charge of the investigation, says he's "absolutely confident" arrests will be made.

Ms Tolley, 30, was viciously stabbed and shot at close range just before midnight on Friday, December 9, 2016. Police described it as an "execution-style" killing.

Snr Sgt Barnett said the list of 12 includes men and women, some of whom were known to Ms Tolley.

At least 15 people have spoken to police with direct knowledge of the planning, killing and cover-up.

"However, up until this point, they have refused to assist police in a way that would help us progress the investigation," Snr Sgt Barnett said.

He said attitudes are "slowly changing" with people coming forward with new information, but there are still people who have spoken with the offenders who haven't come forward to police.

Ms Tolley's mother Cathrine told police: "Words cannot describe how we all feel. It feels like just yesterday that these cowards took her from us, the pain does not get any easier.

"We miss Lois so much - this has devastated our family and her friends, they stole her future from her and all of us."