A former university tutor accused of stabbing his ex-girlfriend was a narcissist who lost control when provoked, a High Court jury has been told.
Clayton Weatherston, 33, is charged with stabbing student Sophie Elliot at her family's home in Dunedin on 9 January 2008.
Mr Weatherston denies murdering Miss Elliot, 22, but has admitted to manslaughter in at the High Court in Christchurch. She was stabbed or cut 216 times.
The defence says Mr Weatherston was provoked by the tumultuous relationship he had with Miss Elliot.
But lawyer Greg King said the defence of provocation does not imply Miss Elliot was to blame for what happened, or lessen the impact of what his client did.
The defence urged jurors to put emotion aside and only focus on the evidence as they consider what drove Mr Weatherston to kill her.
Mr Weatherston, who tutored in economics at the University of Otago, began giving evidence in his own defence on Wednesday afternoon.
In a calm, clear voice Mr Weatherston told the court he was motivated and won numerous academic awards, but was also very short-sighted and upset about having to wear glasses as a child.
"I was terrified at being teased ... Now, glasses are fashionable - but not back then. It was a source of differentiation and possibly derision from other people."
The defence says even though Mr Weatherston went to Miss Elliot's house with a knife he was not a cold-blooded killer, and was provoked when she lunged at him with scissors and knocked off his glasses.
Mr King told the court his client lost control on the morning of the killing. He said although Mr Weatherston had a knife in his bag when he went to meet Miss Elliot, he did not go there to kill her.
The court was told Mr Weatherston suffered from narcissism, obsession and anxiety disorders.
Mr King told the jury Mr Weatherston's personality meant he could not cope with the volatile relationship.
"The accused has features of anxiety disorder and personality features of narcissism and obsessionality. A character trait of the narcissist is the propensity for narcissistic rage when frustrated and, or, humiliated."
The defence says two psychiatrists will give evidence about Mr Weatherston's psychological make-up.
An optometrist also gave evidence on Wednesday, saying Mr Weatherston was unable to see without his glasses beyond 15 centimetres from his face.
Earlier, the Crown closed its case following two-and-a-half weeks of evidence.
