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By the time he killed Sophie Elliott on January 9 last year, former economics tutor Clayton Weatherston was like "a coiled spring", his lawyer, Judith Ablett-Kerr, told the jury in her three-hour closing address yesterday
And the trigger that released that spring was what occurred between him and Miss Elliott in her bedroom when she, in anger and frustration, made insulting remarks about his family, responded to his accusation of infidelity and the need for STD tests and lost the plot herself.
She yelled out "F... you, Clayton" and attacked him with scissors, knocking his glasses off.
Far from being a calm and premeditated attack, Weatherston's response was spontaneous - "horrific but spontaneous" - because of what had gone on before in the relationship and because of the "trigger" in the bedroom.
The Crown accused Weatherston of not taking responsibility for anything, but he had pleaded guilty to manslaughter, a crime second only to murder.
He had accepted responsibility for assaulting his former partner.
Mrs Ablett-Kerr suggested traces of Miss Elliott's blood found on the inside of Weatherston's laptop bag created "a difficulty for the Crown".
They meant the knife had been removed from the bag only after Miss Elliott had started bleeding.
The Crown tried to suggest Weatherston had brought scissors with him to the house as well as the knife, but that allegation was later withdrawn.
The issue for them was whether Weatherston was a cold-blooded premeditated killer, or someone who, as a result of provocation, lost his self-control and committed "this terrible act", Mrs Ablett-Kerr told the jurors.
The defence case was very clear - that he was provoked by the emotional pain of the torrid and tumultuous relationship he had experienced over those months and which he was ill-equipped to deal with because or his own personality makeup.
The Crown said there was no evidence of a downward spiral in Weatherston's condition, and that by January 8 he was having discussions with friends and colleagues about the future but that somehow, on January 9 he woke up "this person with no personality disorders" on his birthday and decided: "Today I will go and kill Sophie Elliott".
Commonsense would tell them "this man is not normal", Mrs Ablett-Kerr said.
Weatherston was a man who was psychologically challenged because of his personality.
"But he's not a psychopath, not a schizophrenic, not on P.
"It doesn't make sense", she said.
What caused the incident on January 9 was Miss Elliott attacking him with scissors, causing him to lose control and in the context of what had happened earlier in the relationship "and that was pretty horrific in itself".
Also on his mind was the question of what damage Miss Elliott's supervisor Robert Alexander could do to his job application.
He suspected Sophie would tell Dr Alexander what had happened during incidents on December 27 and January 7.
Mrs Ablett-Kerr suggested the relationship between Weatherston and Miss Elliott was already a strange one, being between a student and a lecturer with a reputation for challenging people in authority, and disputing issues of co-authorship and plagiarism, but it developed into a relationship with three people, of whom Dr Alexander was the third.
Miss Elliott used him as a "dumping ground" for her complaints about Weatherston and it was clear she thought a great deal of him, writing in her diary she "loved him" [Robert] and he was her "favourite person".
She also wrote that Weatherston said her relationship with Dr Alexander was weird and that he had accused her of sleeping with him, although he immediately retracted that.
The special characteristics relating to Weatherston's psychological makeup were relevant to the defence of provocation, Mrs Ablett-Kerr said.
And the provocative acts were the nature of the background and course of the relationship finally culminating in the events of January 9 when Miss Elliott came at him with the scissors, knocking off his glasses.
His first response to the police when asked why he had killed Miss Elliott was: "The emotional pain she's caused me" over the past few months.
Two psychiatrists said the accused was unusual and had personality characteristics which took him outside the norm, that he had an anxiety disorder and personality features of narcissism and obsessionalism.
Both psychiatrists commented on his inability to express any empathy with the deceased, which was "a clear illustration of his personality characteristics", Mrs Ablett-Kerr said.
There was little doubt he had dissociated from his feeling during the incident - he was at a loss to explain the mutilation.
"He went on stabbing her long after she was dead.
"That was not the action of a man who was normal.
"It was the action of a man who's lost the plot."
But a man could act in a focused and directed way and still not have self control.
"Reluctant as you may be to be drawn to this position, the fact is what occurred in that bedroom was a result of all the provocation that had been simmering underneath and was triggered by that attack on him."
Science and independent evidence backed the defence contention the verdict should be manslaughter, not murder, she said.