House of Horrors killer Jason Somerville says he killed the only person who ever loved him - and cannot understand why.

The 34-year-old was jailed in January for 23 years after pleading guilty to murdering his wife Rebecca and neighbour Tisha Lowry and burying their bodies under the floor of his Christchurch home.

This week the High Court granted the Herald on Sunday access to transcripts of video interviews between a police detective and Somerville.

During the interviews Somerville explained in graphic detail what he did to the women - and why.

He showed no remorse at his High Court sentencing in January and has never offered an apology. But he recognised the gravity of his actions in an interview with Detective Sergeant Darren Folau.

"I don't understand ... that's two lives I know I shouldn't have taken," Somerville told Folau.

"I honestly don't understand it cos it goes against each, everything I've been taught."

The transcripts also reveal that during the interviews:

Somerville recalled his teenage "peeping tom" phase when he watched a neighbour undress through binoculars.

Police had warned him about stalking women after receiving complaints about his daily walks around the Huka Falls, near Taupo, in 2002.

Somerville told how he planned to abduct a social worker to scare her from taking his three children away.

He revealed he was on medication for mood swings.

Rebecca Somerville's uncle Peter Clifford-Marsh said her family would prefer not to know about her killer's past and just wanted him to get help.

"We don't hate him, hate is a pointless emotion," he said.

"He told his uncle, 'I've killed the only person that ever loved me'. He knows what he's done, he's well aware of it.

"We don't think that he's a bad person, he's just a person who's made a mistake. We just hope he gets the help he requires - he needs help."

Lowry, 28, was last seen walking towards her grandfather's home, two doors down from Somerville's, in September 2008.

Somerville was interviewed by police searching for her but was not investigated further.

In September 2009 he made the shocking revelation he had not only killed his wife, who he reported missing days earlier, but was also responsible for Lowry's death.

During three interviews, lasting about four hours, Somerville told police he "throttled" Lowry because she would not leave his house.

"I was outside [chopping] some wood, came in to get a drink, someone was knocking at the front door. It was her," he said.

Somerville let Lowry in and said she walked around the house "looking at things" before going upstairs.

"She's played with the computer I've had set up ... had a look at the filing cabinet. I asked her at that point to leave and she didn't really want to."

He said he pushed her on the staircase but she did not fall.

"I've grabbed her and I've held on to her. I've at some point laid her against the wall ... she was slipping down ... fighting me ..." He held Lowry until she "stopped fighting".

"I knew this person was well and truly a goner cos of how long I'd held her."

Somerville initially denied having sex with her body, saying "that would be sick".

But he later admitted shoving underwear in her mouth, trying to have sex with her and pushing her body into a cupboard under the stairs.

After going to an Alcoholics Anonymous meeting, he came home and pushed her body through a manhole under the house and cleaned up before his wife came home.

The following morning Somerville had sex with the body before burying her under the house. Tragically, Rebecca Somerville met the same fate as her neighbour last August 30.

The couple had been married six years and had two children together.

Somerville's third child is believed to have been born to his wife when she was in a previous relationship.

All three children are in Child Youth and Family care.

Somerville initially told police he strangled Rebecca to stop her hitting him. He later admitted he was "angry' and "rejected" because she would not have sex with him.

"I grabbed her by the throat and held on to her ... I locked her in a headlock ... I snapped ... and then I initially tried to cover my tracks," he said.

Somerville said he didn't expect his wife to die and "panicked" when he came back from the toilet to find her dead.

"When she finally gave up I let go ... I honestly thought she was going to be fine when I let go of her.

"It's the first time I've actually had someone die after I've let them go after doing that. I don't understand why the hell she died, I mean shit, when you let someone go they're supposed to live man."

Somerville also shoved underwear down his wife's throat and once he was sure she was dead, had sex with her before burying her.

"I kissed her on the forehead and said goodbye to her ... I panicked. I dragged her off the bed, dragged her downstairs ... I was more worried about the trouble I would get into and it was ... crazy."

During the interviews, Somerville also admitted he had thought about keeping some of his wife's body parts.

Their house was destroyed in a series of arson attacks after the bodies were removed early last September.

The Christchurch City Council has spent $26,500 clearing 190 tonnes of debris from the site and has obtained valuations and draft agreements of sale and purchase for it.