Mark Lundy told a police officer soon after the bodies of his wife and child had been found he had "been a naughty boy", the High Court at Wellington has been told.
Mr Lundy, 56, is accused of murdering 38-year-old Christine Lundy and seven-year-old Amber Lundy, whose bodies were found in their Palmerston North home on 30 August 2000. The Crown claims Mr Lundy killed his wife for her insurance money and Amber because she saw what he was doing to her mother.
Key points from Day 28:
Detective Jennifer Curran said she was involved in stopping Mr Lundy as he drove back into Palmerston North on 30 August.
She moved his car before driving him to Palmerston North Police Station, where she started interviewing him.
While recording Mr Lundy's movements of the previous evening, he looked at her and said "I've been a bit of a naughty boy".
She asked what he meant, at which point he told her he had hired a prostitute the previous evening. He then went on to talk about his sexual relationship with his wife, Ms Curran said.
Mr Lundy told Ms Curran he and his wife had a close relationship and would "gross nieces and nephews out with our public displays of affection". The couple always worked out their differences, he said.
The family had no business or social problems and had a lot of friends, Mr Lundy said in his statement to the police, which Ms Curran read to the court.
"I get on with everybody ..." he said.
He had spoken to his wife and daughter for the last time about 5.30pm on 29 August, when Amber called to ask if she could have takeaways for tea.
Mr Lundy said his wife cooked only two or three times a year and that she and Amber would have takeaways when he was away.
DNA under victims' nails examined
Earlier today, Marielle Vennemann, a researcher at the Institute of Legal Medicine at the University of Munster in Germany, told the trial DNA from two males was found under Mrs Lundy's fingernails, and from three males under Amber's.
Mr Lundy could not be rule out as the source of that DNA but that would be expected from people living close together, Dr Vennemann said.
She also found similarities in the DNA found under the nails of both and belonging to an unidentified male, she said.
Dr Vennemann attacked the methods a Dutch expert used to conclude a substances on Mark Lundy's polo shirt was brain matter.
Samples from smears found on a polo shirt belonging to Mr Lundy were taken to Laetitia Sijen, from the Netherlands Forensic Institute's (NFI) department of human biological traces, to identify which part of the body they came from.
She told the High Court at Wellington two weeks ago she used an RNA "brain plex" to conclude there was evidence of human brain in one of the smears. It was tested against brain tissue from seven animals, including chicken and cat, to reach the conclusion.
But Dr Vennemann said she agreed with British expert Stephen Bustin that there were a number of issues with the testing procedure.
"I believe it is not fit for purpose," Dr Vennemann said.
Dr Vennemann observed the brain plex being used at the NFI but said she had no control over its design or the manner in which it was conducted as she was there only to watch.
She did query one part of it but was told the test was always done that way and worked well.
"I decided not to push it at this point any further because at this point I did not have all the disclosed material," she said.
Dr Vennemann was also critical of standards at ProPath Laboratories in the United States, where pathologist Rodney Miller created paraffin blocks to create slides for an immunohistochemistry (IHC) technique to look at tissue found on Mr Lundy's polo shirt.
He, too, has identified the tissue as being brain.
Dr Vennemann said she observed work in ProPath's IHC lab for two days and said the standards of cleanliness were not what she was used to.
It was too harsh to say it was a "dirty lab", as suggested by defence lawyer David Hislop, QC, she said. However, it was a "dirty lab" compared with the standards needed for forensic work.
That included dirty benches and equipment not being cleaned between samples, leading to a risk of contamination.
She saw technicians using a microtome to cut slices of paraffin blocks without cleaning it in between samples, and solutions not being changed between samples.
"If you think about DNA contamination, it truly makes your hair stand up."
"So you could have contamination in this lab," Dr Vennemann said.
The trial, before Justice Simon France and a jury of seven men and five women, is in its sixth week.
*Clarification - For the avoidance of doubt, please note that Radio New Zealand reporter Sharon Lundy is no relation to Mark Lundy.