Luc Leclair told jurors Wednesday there is no doubt in his mind that Magnotta is schizophrenic and was not of sound mind during the killing in May 2012.
"Insanity is insanity," Leclair told the jury, using the French word 'folie' multiple times during his hour-long address.
Magnotta, 32, has pleaded not guilty to first-degree murder and four other charges stemming from Lin's slaying.
The native of Scarborough, Ont., has admitted to causing the death of the 33-year-old Chinese engineering student, but is seeking a verdict of not criminally responsible by way of mental disorder.
Leclair said many of Magnotta's actions and much of his behaviour before and after the slaying can be attributed to that "madness."
While the Crown has suggested Magnotta was of sound mind, Leclair sees it differently.
The case against Magnotta showed he kept Lin's baseball cap, with the prosecution theorizing it was a sort of trophy. The Crown also showed apartment surveillance video where the accused was seen methodically emptying his apartment in the wee hours of the night.
Leclair said these details aren't evidence of premeditation but rather a byproduct of his madness. The lawyer cited other examples over the years: Magnotta claiming to hear from Marilyn Monroe or fuelling a rumour he was romantically linked to Karla Homolka.
"Everything suggests it's insanity," Leclair said.
Prosecutor Louis Bouthillier, who will give his closing arguments Thursday, has said the crimes were planned and deliberate.
Leclair asked jurors to put themselves in the mind of the accused in coming to a decision.
"Insanity is something that you're going to have to live," he told them. "You're going to have to put yourself in the head of Mr. Magnotta."
He said the verdict should be the same for all five charges.
"Other verdicts are possible, but I'm asking you to declare Mr. Magnotta not criminally responsible," Leclair said.
In addition to premeditated murder, he's also charged with criminally harassing Prime Minister Stephen Harper and other members of Parliament; mailing obscene and indecent material; committing an indignity to a body; and publishing obscene materials.
The jury heard 66 witnesses over a 40-day period, including half that time spent on the reports of forensic psychiatrists who had different views on Magnotta's illness and state of mind at the time of the crime.
Leclair suggested to the jury they consult the various expert reports but not get bogged down by them and turn the case into a battle of experts.
"You must use your good sense and your life experience," Leclair said.
Magnotta did not testify at the trial and did not submit to an evaluation by the Crown's own forensic psychiatrist.
Leclair said that shouldn't count against his client, who has a right to silence and wasn't obliged to speak to the Crown expert, Dr. Gilles Chamberland.
Leclair said Chamberland was biased and had preconceived notions about Magnotta that he discussed in 2012 media interviews where he called the accused a "psychopath" and "perverse."
The defence lawyer suggested the jury simply set aside Chamberland's testimony altogether.
Magnotta's medical file shows he was diagnosed with schizophrenia in 2001.
Chamberland has countered it's possible there was a misdiagnosis that was simply carried forward over the years and that Magnotta actually suffered from a variety of personality disorders. Leclair called that far-fetched.
"It is impossible that there was a conspiracy among psychiatrists for 10 years," he told the jury. "That would be absurd."
Neither sympathy nor pity has a place in this case, Leclair said, be it for his client or the victim. Neither does a feeling that Magnotta deserves to be punished. Instead, the lawyer implored jurors to look at the physical evidence in the case.
Leclair called the case unique in that the jury has access to video evidence that shows Magnotta before and after the slaying.
He also dismissed any similarity between his client's acts and scenes and characters from the film "Basic Instinct," which the Crown has suggested served as an inspiration for the crime.
Leclair said no ice pick was used in Lin's murder and there was no dismemberment, threatening notes to political parties or video recording of the crimes in the movie.
"The similarities are superficial," Leclair said.
He reminded the jury that, while it is up to the Crown to prove all charges beyond a reasonable doubt, the mental disorder defence hinges on a balance of probabilities.
"The verdict of Mr. Magnotta is in your hands," he told the jury before sitting down.
The 14 jurors listened intently as Leclair delivered his final arguments, while Magnotta kept his head low and listened to his lawyer through a translator as he spoke in French.
Justice Guy Cournoyer will give his final instructions Friday.
Only 12 jurors will deliberate.
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