"There's no doubt she was murdered but who was her killer?"

That's the question Justice Joseph Williams has put to jurors this morning as the Mei Fan murder trial concludes.

Michael Edwin Preston, 60, is accused of murdering Ms Fan, his estranged wife, at her Wellington home on Friday November 8, 2013.

At the High Court in Wellington, Justice Joseph Williams told the twelve jurors "a wealth of evidence" was available for them to sift through.

The trial began five weeks ago, and frequently heard graphic, bloody, and highly emotional testimony relating to the death of the 37-year-old mother.

Justice Williams gave the jury the usual advice - to consider evidence carefully, ignore outside reports, and not allow any feelings of prejudice or sympathy to influence their deliberation.

He also acknowledged the tragic impact Ms Fan's death had on her and Preston's children.

"They were caught up in a nightmare scenario not of their making and probably not fully understood."

The judge said he could imagine jurors felt sorry for Ms Fan - and he did too - but that didn't mean Preston was guilty.

Justice Williams said Preston was easily seen as a person of "eccentric character" who could come across as not very likeable.

That too, the jurors would have to ignore.

And the judge recalled the often caustic arguments that characterised Preston and Fan's relationship.

"Nasty things were said and done, including nasty things by Mr Preston."

But that too, the jurors would have to disregard.

"Whether you like Mr Preston or not is utterly irrelevant."

The Crown case is that Preston killed Ms Fan in a frenzied knife attack in the suburb of Miramar to gain sole custody of the couple's two children.

Preston denied this, and denied breaching a protection order Ms Fan had taken out against him.

On Friday, Crown prosecutor Grant Burston said Preston had "three windows of opportunities" to kill Ms Fan, whose body was found on her laundry floor with multiple stab wounds on the Sunday after her death.

Mr Burston alleged the 60-year-old had "targeted" Ms Fan's neck and face as she was stabbed 15 times.

He added the person who killed Ms Fan must have "really hated" her.

"He had finally had enough. He stabbed her 15 times in the neck with a carving knife and left the knife there," he said.

But defence lawyer Louise Sziranyi urged the jury to keep an open mind.

She said there was no direct forensic evidence to suggest Preston killed his estranged wife.

Ms Sziranyi acknowledged the murder was a "tragic and horrific event" but said Preston was genuinely distressed when he realised his two children weren't picked up on the day of Ms Fan's death.

Justice Williams said if the jury found Preston guilty of murder, he'd "obviously" be guilty of breaching the protection order too.

Likewise, a murder acquittal would necessitate an acquittal on the other charge.

The judge said it was clear Ms Fan was stabbed to death in her home.

"We know that Ms Fan suffered 38 stab...wounds in total."

These included "multiple defensive woods" on body parts including her arms.

"...The last straw, the Crown says, was legal service of the second temporary protection order," the Judge added.

"The defence says you cannot be sure Michael Preston committed this crime."

The court heard that Preston's communications after Ms Fan's death were intercepted on 1100 occasions

Justice Williams said there was no doubt the Crown case was circumstantial, with no direct evidence Preston was at the Brussels St house when Ms Fan was brutally killed.

"Rather, the Crown invites you to infer certain things."

These inferences included the idea Preston had a motive to kill his estranged wife.

Justice Williams said the defence also argued there was no way Preston had time on that Friday morning to visit Miramar, kill Ms Fan, and dispose of his blood-soaked clothes and other incriminating evidence in the window of time available to him.

He said another defence argument hinged on the suggestion the killing was not "personal" and Ms Fan's body was not defaced or mutilated.

"Rather, this killing was clean."

The judge urged the jury to treat as irrelevant evidence of a religious note found at the crime scene.