Chris Kahui's defence team is to make a formal complaint about the police handling of his sons' murder inquiry.
Mr Kahui's lawyer, Lorraine Smith, said today that she and co-counsel Michele Wilkinson Smith would lodge a complaint with the Independent Police Complaints Authority, probably next week.
On Thursday,a High Court jury in Auckland found Mr Kahui not guilty of murdering baby twins Cru and Chris two years ago.
Mrs Smith said the complaint would be over the time that police took to disclose to the defence some of the evidence they had gathered.
"We were furious," she said of the delay.
She said an interview that police conducted with Eru Tuari, who had had a relationship with the twins' mother, Macsyna King, was not disclosed to the defence until six months later.
In court, Mr Tuari said in his testimony that Ms King had told him that "Chris didn't do it, I did it", which he interpreted as a confession.
At the trial, it was also revealed that police knew about a cellphone call made by Ms King's sister, Emily, that placed Ms King in Mangere about the time the twins were assaulted in a house in the suburb.
Ms King had told police she was with her sister that night and they were not anywhere near Mangere.
"The police picked up on the cellphone call in Mangere early in the piece and they went in and interviewed Emily about it and didn't disclose any of that to us," Mrs Smith said.
"The police left it because it did not fit their theory."
She also said she was upset by inquiry head Detective Inspector John Tims' response after the trial when he was asked about her criticism of the police inquiry being a "disaster".
Mr Tims, speaking at a news conference, said Mrs Smith's statement in her closing address to the jury could have been made for the "purposes of the courtroom".
"I was really annoyed about that," Mrs Smith said.
"That's not my style. You don't slate off people just to get an effect, you just don't. He knew that wasn't the case and to say that to the media was unfair and improper."
Mrs Smith said she stood by her use of the word "disaster" to describe the police investigation, which had Mr Kahui as the sole murder suspect.
"Yes, absolutely, because they closed their minds to any other possibility."
Meanwhile a close friend of Chris Kahui is pleading with police to reinvestigate the murders of Kahui's twin sons.
Pastor Tom Ngapera, who Mr Kahui lived with for almost two and a half years, says somebody should be held accountable.
"The family is concerned, I'm concerned, people in New Zealand are concerned because we know that somebody did it," Pastor Ngapera said.
"That's what's been established in the courthouse. Medical professions gave their opinions. Somebody did it."
Pastor Ngapera denies there was ever a whanau wall of silence around the deaths as he says the whole family was interviewed.
He says the Kahuis' want a sense of closure and he is hoping for the day when somebody cracks and tells police what really happened.
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Video: Chris Kahui after being found not guilty