Mr Burston alleged the 60-year-old had "targeted" Ms Fan's neck and face as she was stabbed 15 times around the area.
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
The Crown said a critical piece of evidence was strands of polypropylene fibres or synthetic hair found around and on Ms Fan's body.
Mr Burston said the synthetic hair found was similar to that from a Halloween witch hat worn by Preston's daughter.
Ms Fan and Preston's daughter told Police she wore a witch hat with strands of synthetic hair for Halloween in 2011 and last saw it in a cupboard at Preston's property in Ahuriri St.
When police searched Preston's property, the hat was not found.
Mr Burston claimed Preston needed a way for Ms Fan to open her front door on the day of the murder.
By claiming he had to give his child her Halloween costume, Ms Fan would have opened the door, Mr Burston said.
"It would have concealed the knife.
"It was a way to get close enough to strike her with a knife," he told the court.
Mr Burston also dismissed the other suspects of murdering Mei Fan, including her partner at the time Tani Hoyhtya , her uncle, a burglar and a professional hit man.
The Crown said the burglar theory was "nonsense".
He questioned why a burglar would pick an "obviously occupied house".
He also asked why a burglar wouldn't take valuables in the house such as a phone and a tablet.
The Crown also added the door was locked and questioned why a burglar would do this.
"The burglar didn't know her children would come home that day through the same door," he said.
Mr Burston claimed the ransacked bedroom photographed at the scene was staged by Preston to make it look like a burglary.
He said Ms Fan lied to Preston when she was in China, by stating her uncle was threatening to kill her as she had wanted to come back to New Zealand to be with her children.
Mr Burston said there was a "long history of a toxic relationship" going back to the couple's time in China.
He said the toxic nature was evident through text messages exchanged by Preston and Ms Fan, and also his attempt to deport her back to China.
He added Preston had admitted "they were going through a terrible, terrible custody battle".
He said the couple had played a game and Ms Fan was winning.
Two months before her death, she was focused on her children and was becoming independent.
Mr Burston said he was determined to get full custody of his two children.
"The stakes were very high for him."
The Crown said when Police turned up at Preston's house, he simply broke down and cried.
"He didn't ask what happened."
"Right from the start he was pointing to other suspects," Crown said.
Mr Burston said he pretended Ms Fan committed suicide instead.
However, "once the knife came out she didn't have a chance," he said.
Defence lawyer Louise Sziranyi urged the jury to keep an open mind.
She said there was no direct forensic evidence to suggest Preston had killed his estranged wife.
"This is a circumstantial case," she said.
Ms Sziranyi acknowledged the murder was a "tragic and horrific event" however encouraged the jury to focus only on the day of the murder on November 8, 2013.
She dismissed the Crown's argument of Preston concealing a knife in his child's Halloween witch hat.
Ms Fan had just got a protection order issued to her husband.
"If she saw him walking up the driveway she would have called 111 straight away," she said.
"It calls for speculation from the highest order."
The defence also dismissed the Crown's argument a wig was involved in the murder.
She said no propylene fibres were found in Preston's property, including his car.
"Not one fibre was found."
She said Police looked in wheelie bin and Preston's vacuum cleaner but "not one strand was found".
She stressed the hat was a $2 item and two out of four wigs tested by Police matched the synthetic hair found on Ms Fan's body.
The defence said Preston was genuine and distressed when he realised his two children weren't picked up on the day of Ms Fan's death.
She said if he had killed his wife, he "would have been so cunning and so clever" he would have driven by the school and picked up his children.
The family court file showed Ms Fan never made a complaint that Preston had threatened to kill her.
The defence said Family Court had said the custody arrangements at the time "worked well" and there was no evidence he would lose time with his children.
Ms Sziranyi reiterated Ms Fan hadn't applied for sole custody and therefore there was no motive from Preston to kill his wife.
She said Preston had no idea he was under heavy surveillance that included his best friend being wired.
He was also unknowingly filmed when he viewed Ms Fan's body.
She said Preston had a offbeat, quirky persona and often made inappropriate comments.
She reiterated this was who he was and did not make him a murderer.
"It is his melodramatic way of communicating," she said.
