When two detectives knocked on Linda West's door and told her that her son had been murdered, she knew straight away who the killer was and gave them a name - Dionne Liza Neale.

Mrs West had come to know 39-year-old Neale, a hairdresser turned prostitute, when she began dating her son Reece Shadbolt.

Mrs West and the rest of Mr Shadbolt's family initially welcomed her and included her in family celebrations.

Now she can't even bring herself to say her name, referring to Neale as "the offender" or "she" when reading her victim impact statement to the High Court at Auckland at Neale's sentencing for Mr Shadbolt's murder.

Mrs West said her "whole world as I knew it" shattered when police told her her son was dead.

"I felt a terrible pain in my chest ... It was as if my heart was breaking in two. The air was sucked out of me and I felt the shock down to my feet."

Struggling to breathe and shaking, Mrs West said she told police straight away who had killed her son.

"I knew who did it and told them who did it."

She spoke of her "gut feeling" something was wrong during the last six months of the couple's relationship. Neale's demeanour and behaviour changed; sometimes moody, sometimes fine - and other times intense.

During the trial the court was told Mrs West urged her son to change his locks.

He said that he would because he didn't want Neale to do a "Mrs Bobbitt on me" [cut off his penis].

His murder had robbed two children of their father and changed the dynamics of the extended family.

"I'll never forgive her for the havoc she has caused in so many lives ... His children will never have their dad. How dare she."

The last time she spoke to her son - "before she took him" - he told her he was going to play golf.

Neale stabbed him nine times in the chest, shoulder, throat and neck but it was the first wound that sliced his heart and lungs that killed him.

He was in the shower, on Waitangi Day 2007, and the couple had just argued about his continued use of prostitutes.

Artistic and athletic, he had worked in the advertising industry and his family felt he had reached the pinnacle of his career.

"He was a loving, loyal son and we had a special understanding."

Mrs West said the two-and-a-half-year wait from murder to sentencing was cruel. During the trial she had heard things a mother should not have to hear.

Justice Graham Lang told Neale that after listening to Mrs West she knew what havoc and devastation she had caused.

When the judge said it was a tragedy for her as well, Neale said softly, "Yes."

He sentenced her to life in prison with a minimum non-parole period of 10 years, to loud applause from supporters who wore T-shirts bearing Mr Shadbolt's photo.

Prosecutors did not seek an extended term beyond the mandatory 10-year sentence.

Neale's lawyer, Barry Hart, told the Weekend Herald that he would appeal against the conviction.

"She is a normal, nice person. This is a tragedy for her as well as the deceased."