A central figure in one of Waikato's most baffling cold-cases has admitted killing Kerepehi woman Sara Niethe.

Mark Pakenham, her former boyfriend, has today admitted a charge of manslaughter.

Pakenham was charged with her murder but pleaded guilty to a reduced charge at the High Court in Hamilton.

The Auckland beneficiary is the brother of senior police officer Brett Pakenham.

Pakenham's plea could clear the way for Niethe's family and friends to finally get answers to the almost decade-old mystery.

Niethe, a mother-of-three, has not been seen since visiting Pakenham's Kaihere home 35km northwest of Morrinsville in March 2003.

Pakenham, who was interviewed by police just days after her disappearance, alleged the couple had spent the evening drinking, smoking and having sex before a brief argument.

The next day Pakenham visited Niethe's house and handed her youngest daughter, Danielle, her mother's sunglasses, phone, cigarettes and lighter, saying her mother had left the items at his house the night before.

Niethe borrowed her mother's Honda Civic hatchback car on the night she disappeared.

Despite an extensive search of roadside waterways, swamps and banks across the Hauraki Plains, neither Niethe or the light blue Honda Civic were found.

A $50,000 reward posted in 2003 also failed to shed light on Niethe's disappearance.

In 2010 police conducted a full review of their investigation and, following that, an extensive reinvestigation was launched.

Evidence assembled by the investigation team was reviewed by the Hamilton Crown Solicitor before a decision was made to arrest Pakenham in August 2011.

Niethe had only lived in Kerepehi for a year before her she disappeared.

THE SARA NIETHE FILE

March 30, 2003: Sara Niethe last seen leaving friend Mark Pakenham's house in Kaihere, heading for Kerepehi.

April 5, 2003: Search and rescue teams begin a three-day search along the roads Niethe might have taken home but find nothing.

May 10, 2003: Pakenham speculates Niethe may have been abducted after leaving his house on March 30. He denies any involvement.

July 23, 2003: A witness reports seeing Niethe's car being driven erratically near Ngatea on the night of Niethe's disappearance.

September 26, 2003: A $50,000 reward offered for information leading to Niethe, her car or an arrest. The reward is unclaimed.

August 22, 2008: Psychics Deb Webber and Sue Nicholson suggest on television show Sensing Murder that Niethe was beaten and murdered after a drug deal turned sour. Police say they need more information before reinvestigating the case.

August 18, 2011: Pakenham is charged with Niethe's murder.

February 15, 2013: Pakenham appears in the High Court at Hamilton and pleads guilty to Niethe's manslaughter.

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