Earlier Mrs Ablett-Kerr told the jury Sophie Elliott must have kissed Weatherston when he arrived at her house the day he killed her, because that was the way they were.
"They couldn't just end it, they would have terrible row and make up."
If Sophie Elliott really believed he had assaulted and attempted to rape her earlier there was no way she would invite him up to the bedroom, Mrs Ablett-Kerr said.
Sophie might have told her mother Weatherston was just sitting there, because she might not have wanted to tell her mother what they were discussing.
Mrs Elliott said she did not hear anything until she heard the screaming, Mrs Ablett-Kerr said.
"With great respect and due deference to her . . . but what she saw on that day must make her a less than reliable witness as far as details go.
"I don't want to say that, but I do because I have to."
This conversation actually did take place in the bedroom. She was downstairs when the flush went. Sophie goes upstairs after the flush has gone and Clayton Weatherston goes in to the bedroom, Sophie goes in to the room. She was the last person in.
You know that the scissors must have been used first, that is the only way you can account for the scientific evidence. The only way.
"Members of the jury, reluctant as you may be to ignore this position, the fact is that what occurred in that bedroom was as a result of Clayton Weatherston losing all control, after he was provoked by the attack on him."
You will want to fight it, but you can't because the science supports it, the relationship which you have independent proof of supports it. Sophie's own writing supports it and tells you that what the defence is saying too is what happened. And it is terribly, terribly said, it's tragic. It's awful."
The jury's duty was to bring in a verdict in accordance with the evidence.
"The evidence is that manslaughter was committed here, not murder."
Earlier, Mrs Ablett-Kerr told the jury Clayton Weatherston was not normal.
"Well, you saw him. You saw him over five days. Did you think he was haughty and arrogant? Did you get the picture of him as a normal sort of guy? I doubt it."
The 33-year-old former economics tutor stabbed Miss Elliott to death in her Ravensbourne home on January 9, 2008, inflicting 216 separate wounds with a knife and scissors. He denies murdering her but admits her manslaughter, saying he was provoked into losing self control.
Was he a cold blooded murderer or was he someone who as a result of provocation lost his self control and thereby committed this terrible act?, Mrs Ablett-Kerr asked the jury.
They must decide if the Crown had disproved the latter, she told them.
By January 9, Weatherston was like a coiled spring, and the trigger that unleashed that spring and set it loose was what happened in that room.
"When Miss Elliott, no doubt frustrated herself, . . . attacked him with a pair of scissors. That was the straw that broke the camel's back."
Far from being a deliberate, planned, calm, premeditated attack, the defendant's response was spontaneous.
It occurred because of what had gone on before and the trigger in that bedroom.
"Can there really be any other explanation for what occurred?
"This man is not normal. He won't like some of the things I am saying, but they have got to be said because they are there and they are true?"
"What would make a man with a future ahead of him wake up and say 'today's the day I'm going to kill Sophie Elliot'. What kind of sense does that make?"
There were three people in the relationship, Mrs Ablett-Kerr said.
"Clayton Weatherston, Sophie Elliott and Robert Alexander."
Excerpts from Sophie Elliott's diary revealed how she felt about her supervisor, and how she felt like she was in the middle of Dr Alexander
and Dr Weatherston. Dr Alexander had run down Weatherston to her and vice versa.
"What is this man doing talking to this student he is supervising and running her boyfriend into the ground?"
Sophie Elliott was caught between the two, a dangerous position she should not have been put in, but both did.
Alexander had made it clear to Sophie that, despite others in the department thinking Weatherston should get a lectureship, he did not think
he should. Miss Elliott had relayed that information to Weatherston.
The consequence was that the coil inside Weatherson became tighter and tighter.
Earlier, Mrs Ablett-Kerr told jurors they must put aside emotion and apply the law of the land.
The challenge was to resist emotion, sympathy and prejudice for they were the enemies of justice, she said in the High Court in Christchurch.
"The jury must resist anger and revulsion," she said.
"They must listen to the questions and the answers and be very careful about what they heard. Be very careful about what you are looking for. You are looking for the truth."
Earlier, prosecutor Robin Bates told the court the provocation argument Clayton Weatherston has used in his defence did not fit in with the order of how things happened the day he stabbed Sophie Elliott to death.
The accused had told too many varying stories, prosecutor Robin Bates said.
"Unfortunately when you do that inconsistencies creep in and you start to make mistakes, and that is what has happened.
The accused's insecurities and anxieties about wearing his glasses were the normal insecurities and anxieties of a child or a teenager growing up and the suggestion he was vulnerable because of his glasses did not wash, Mr Bates said.
That he, who worked out regularly, felt threatened by someone so much smaller and weighing 30kg less than him, also did not wash.
The Crown suggested Sophie knocked the accused's glasses off as she tried to defend herself. There were defence wounds from the knife on her arms.
There was no scissor attack, and therefore no provocation.
"It really comes down to scissors or nothing in relation to proving he was provoked."
The Crown also argued the accused did not lose his power of self-control.
The assumption was that he must have had to have stabbed someone 216 times, but you could not get away from the fact the attack related to specific areas of beauty and sexuality.
Cutting off hair did not injure someone or wound them, so why do it? The injuries indicated purpose, rather than a loss of self-control, Mr Bates said.
His demeanour during and after the killing was calm, Mr Bates said.
He had calmly turned around and closed the door when Mrs Elliott opened it, the police officer first on the scene said he appeared calm and in control.
He was not shaking. He gave details quickly, calmly and had clear recall of details.
On January 8 the accused was still part of a normal, functioning family, just graduated PhD, on the short-list for a job he wanted, and had many friends and a new girlfriend.
That did not fit with what defence psychiatrists had said about his psychological problems.
The accused's behaviour indicated what was on his mind.
He had told Sophie he wished she was dead, told other people he hated her and was not going to be controlled.
"If you put these matters together, the picture painted was that this was premeditated," Mr Bates said.
Weatherston had carefully, systematically killed her, was in a calm state straight after and had a total lack of remorse and regret.
"Not only that, he continues to blame Sophie Elliott."
The only conclusion to draw from that was that he had done exactly what he intended to do, Mr Bates said.
It was telling that when asked if he regretted his actions, he said there were many things he regretted.
"He couldn't say he regretted Sophie's death and mutilation because, the Crown says, he did what he set out to do.
"On that basis, the appropriate verdict was guilty of murder," Mr Bates told the jury in conclusion.
The defence will commence its closing argument at 1.50pm.
Earlier, Mr Bates told the court Weatherston had already decided what he was going to do when he locked the door to Sophie Elliott's bedroom.
It simply defied common sense that having gone downstairs to talk to her mother, and accepting advice to get rid of him, that when Sophie went back upstairs she locked the door, presecutor Robin Bates said in his closing address.
"That cannot be the case."
Then when the door was opened by Mrs Elliott, Weatherston reached around, closed it and locked it again.
It was locked in the first place because he did not want to be disturbed,and was locked again after Mrs Elliott opened because he still did not want to be disturbed, Mr Bates said.
'Why doesn't he want to be disturbed? Because he hasn't finished what he set out to do. The locking of the door indicated that he had made up his mind, certainly as he locked the door the first time.
"It is shortly after we hear the scream and that scream has to be when he is going at her with a knife."
Earlier, Mr Bates said Weatherston clearly lied about the events of January 9 when he killed Sophie Elliot.
When Weatherston arrived at the Elliott's house on January 9, he said Miss Elliott kissed him on the lips, which could not be true, Mr Bates suggested.
"This is despite a major row the previous day...the Crown says that didn't happen because Mrs Elliott did not see it.
"She was aware of the situation between them, if she had seen a kiss between them, wouldn't you have thought she would have said?"
When she went down briefly she told her mother the accused was "just sitting there" and not saying anything.
However Weatherston had said they had been having a discussion before that.
"It does not make sense. There is no reason for Sophie to lie to her mother, there's no reason for Mrs Elliott to make that up."
The accused said they then had another discussion on a number of topics.
There was no time for a discussion that long, because within a very short time after Sophie went back upstairs Mrs Elliott heard her daughter yelling.
More importantly, Mrs Elliott did not hear the words "F... you", which the accused claimed were yelled.
When she was asked, Mrs Elliott described the words as being said "very, very loud" and either being 'stop' or 'don't Clayton'.
Mrs Elliott said her daughter had sounded really frightened and once she started screaming it was a "pain scream".
It was not a scream of anger, Mr Bates said.
Mr Bates has told the jury in his closing address that Weatherston went to the house with a knife, which he said he carried constantly in his bag for safety.
However his former girlfriend, who had looked in the bag often, had never seen it in his bag.
He never mentioned to her he was concerned for his safety.
"That is rather strange to say the least. And why not take a smaller knife, or a pocket knife.
"The accused had said it was his weapon of "comfort or choice". "That's a strange thing to say too," Mr Bates said.
He said he was driving around the block looking for Sophie's car, but the Crown suggested he went home and got the knife at that time.
The most telling thing was that went up to the door when he could not see her car at home, Mr Bates said.
Why did he not leave the presents at the door when he could have done that in a couple of minutes.
He locked the car, yet he took the bag and the knife with him to the door.
"Why? Because he has in mind what happens a few minutes later.
"It's not just coincidence that he's at the door and is carrying a knife and a few minutes later Sophie is dead."
He took the knife when there was no logical or sensible reason to do so.
"Is it just coincidence that the accused has been telling Sophie he wanted her dead and telling other people he hated her?"
Before prosecutor Robin Bates began his closing address Justice Potter said a slim volume of entries in Sophie Elliott's electronic diary had latterly been ruled as admissible and could be referred to in closing arguments.
She also reminded the jury to ignore media reports on provocation or the trial. "The evidence upon which you must decide this case is the evidence you hear in court and only incourt." Mr Bates said he expected his closing to take 1.5 hours.
Mr Bates told the jury a "really critical" part of their task was to observe witnesses and assess the reliability and credibility of what they said.
Circumstantial evidence was used to describe evidence relating to particular circumstances, it was not inferior evidence, in fact it could be compelling.
It was important to look at the picture painted by that evidence, and draw reasonable inferences using common sense.
Any word or act could amount to provocation, Mr Bates said.
That word or act must have the effect of depriving the offender of the power of self control in inducing him to commit the killing.
Thirdly, the act or words must in the circumstance of the case be sufficient to deprive the ordinary person, with the characteristics of the offender, of their self-control.
The Crown says the evidence shows the accused made a deliberate calm and premeditated decision to kill Sophie Elliott either before he went to the house or shortly after he arrived.
The Crown says the alleged attack by Sophie Elliott with scissors was illogical and unproven.
The Crown would take the jury through evidence that would show Weatherston did not tell the truth and wanted to shift responsibility.
The first example was the sitting on and kicking of his former girlfriend.
The former girlfriend had talked about the incident and things he had said in the past, attacks on her intelligence and her looks and two kicks he gave her were hard and then he jumped on her neck and shoulders.
He took her car keys so she could not leave because he wanted to talk about it. She felt trapped, because she was not allowed to leave.
He had tried to blame her for the incident.
As a witness she was intelligent, sensitive, reluctant to misrepresent any situation.
"There was not a mean bone in her body."There was no question she was recounting the incident accurately, Mr Bates said.
"The accused could not recall the incident clearly, but remembered "jumping over her, clipping the top of her head".
"He suggested it was some kind of accident." There he is putting a spin on the situation , turning itaround."
He conceded it was reckless, but he did not intend to hurt her.
In the relationship with Sophie, the accused tried to suggest that Sophie was far more experienced at running this relationship and getting it under control.
That was a misrepresentation of the situation.
Weatherston had several short and long-term relationships before meeting Sophie.
"He is in a situation in university where there are young women all about him and he has had significant experience, I suggest."
He had no qualms in overlapping his relationships either, Mr Bates said.
"It is totally wrong, in the Crown's assertion, the accused as being vulnerable given his age, his experience, his relationships."
