He told the Herald shortly after her disappearance that he prayed for her safe return.
But in 2011 he was arrested for her murder. The charge was reduced to manslaughter by the Crown Solicitor ahead of Pakenham's trial which was due to start in May.
Ms Niethe went missing after leaving Pakenham's house in Kaihere, 35km northwest of Morrinsville, Waikato. She was heading back home to Kerepehi, about 10 minutes drive away.
Police initially thought she might have had an accident so combed canals and riverbanks in the Hauraki Plains area but found nothing.
As the days wore on and her daughter Danielle reached her 10th birthday, police discounted suggestions Ms Niethe had left home.
She had planned her daughter's party at the L&P Cafe in Paeroa to the last detail and would not have missed it.
Inquiry head Detective Sergeant Glen Tinsley said police were hopeful Pakenham would "show some compassion for the family and let us recover Sara's remains".
"We want to comment on the patience the family has had over the 10 years with the police and the conducting of the inquiry."
Mr Tinsley said there were mixed emotions about Pakenham's guilty pleas, which included two charges of injuring with intent to injure two other women in Auckland between 1990 and 1992.
"It's bittersweet but our determination is all around getting Sara back. We remain hopeful but we've got no crystal ball here."
It was still unclear exactly what happened the night Ms Niethe disappeared and Mr Tinsley would not elaborate because a summary of facts had not been agreed between the Crown Solicitor and Pakenham's lawyer, Paul Mabey, QC.
Ms Niethe's family, including her daughter Danielle and mother Eileen Marbeck did not speak to media outside the court.
Pakenham was remanded in custody and will reappear in the High Court on June 28 for sentencing.
