David Mahon's defence barrister has appealed to the jury in his trial for the murder of 23-year-old Dean Fitzpatrick to find him not guilty, claiming the prosecution's case is threadbare and full of exaggerations.
In his closing statement this afternoon, Sean Guerin said Mr Mahon had no motive to kill and every reason not to kill.
Mr Mahon, 45, denies murdering Mr Fitzpatrick on 26 May 2013.
He claims his stepson walked into the knife outside the apartment where he lived with Mr Fitzpatrick’s mother at Burnell Square, Northern Cross.
Mr Guerin said suicide is not the defence's case but suicide or self harm is a possibility.
He told the jurors they will have to weigh up or consider why Mr Fitzpatrick would have done that.
He said maybe it was simply an accident and Mr Fitzpatrick did not see the knife.
Maybe, he said, "it was a stupid, pointless and terrible accident".
But he said there is a second, darker, more troubling possibility; that Mr Fitzpatrick intentionally impaled himself in the knife "seeing only darkness and despair in his life".
Mr Guerin said Mr Fitzpatrick had a history of mental illness, had previously self harmed and had voiced a death wish.
Mr Guerin said just 30 minutes before Mr Fitzpatrick went to Mr Mahon's apartment he received a text message from his girlfriend saying she was under the impression he had cheated on her.
Fifteen minutes later she texted Mr Fitzpatrick again saying their relationship was over and she was with someone else. It was a text, the court heard, that was designed to hurt him.
He said Mr Mahon has admitted the stabbing was his fault but said it is not the jury's role to decide if he is at fault but to decide if he bore criminal responsibility.
Mr Guerin said that Deputy State Pathologist Dr Michael Curtis had "no difficulty in reconciling Mr Mahon's account of what had happened with the science".
He said the prosecution's case is full of hyperbole, hysteria and hypocrisy and asked the jury to find his client not guilty.
The judge this afternoon began giving her charge to the jury.
Ms Justice Margaret Heneghan said the jury cannot attach any significance to the fact that Mr Mahon did not give evidence.
She said there was no reason why he should, as the onus of proof is on the prosecution.
Ms Justice Heneghan said there are three verdicts open to the jury: guilty of murder, not guilty of murder but guilty of manslaughter, or not guilty.
She will continue with her summation of the evidence heard during the trial tomorrow morning.
