Closing arguments have begun in the trial of David Mahon, who is charged with murdering his stepson almost three years ago.
The 45-year-old has denied murdering Dean Fitzpatrick on 26 May 2013.
Mr Fitzpatrick, 23, received a stab wound to the abdomen outside the apartment that his mother shared with Mr Mahon at Burnell Square, Northern Cross.
He bled to death. The prosecution described it as a "gutting" in the opening speech to the Central Criminal Court.
In his closing argument this morning, prosecuting counsel Remy Farrell said the stabbing took place in a split second but the jury would have to look at the surrounding hours and minutes to see what was going on in Mr Mahon's mind.
He said it was clear that Mr Mahon was being aggressive and frenetically trying to contact Mr Fitzpatrick and had made earlier threats to stab.
He referred to the numerous phone calls and text messages sent by Mr Mahon in the run-up to the incident.
"The defence would have you believe it is simply an unfortunate coincidence and that he did just that very thing that he had threatened to do."
He asked the jurors to put themselves in Mr Mahon's shoes and assess why, if it was an accident, did he leave the scene and tell a friend he thought Mr Fitzpatrick was dead and that the knife had gone through him without ever mentioning it was an accident.
He said Mr Mahon's contention that the killing had been an accident and that Mr Fitzpatrick had walked onto the knife was a story he cooked up later for gardaí.
He also said the evidence of the pathologist was the knife entered Mr Fitzpatrick with moderate or considerable force.
He said the jury should think about that in the context of what he describes as having happened.
"Whatever problems Dean Fitzpatrick (below) had you might struggle with the idea that someone would choose that exact moment when a step father produces a knife to decide this is it, I'm going to end it here."
Mr Farrell said this was a fantastical suggestion.
"Bear in mind when it is suggested to you that he assisted the gardaí by talking to them that he left the scene [and] spent time trying to avoid CCTV. Who was he trying to assist? I suggest he was trying to assist himself."
"I invite you to apply common sense to look at what he says.
"He says it was an accident or suicide. What he said was lie, after lie, after lie and all of the lies were absolutely central to the stabbing, they were critical lies, the interviewees are littered with multiple lies. This was a tissue of lies."
"The fact of a lie is somewhat interesting, the reason for the lie tells you a lot more. The number of lies in this case told by David Mahon is quite remarkable and you will have no doubt that those lies point to guilt."
Mr Farrell said Mr Mahon told gardaí that running and hiding was not his style but that is exactly what he did.
He said he also told gardaí that the incident was on CCTV but he knew well there was no CCTV in the area.
"Is this a man who is really there to assist gardaí? Why is it he is trying to mislead gardaí about this?"
"Do any of you believe that all those frantic calls to Dean Fitzpatrick were just to have a chat? To get sense into him? He didn't get sense into him, he got a knife into him in fact. Why was he lying about the reason he wanted to see him?"
He said Mr Mahon's contention that Mr Fitzpatrick had pulled a knife on him in the apartment had not been noticed by his friend Karl O'Toole who was merely feet away.
He said Mr O'Toole said the first time he saw a knife was when Mr Mahon returned to the apartment holding one.
Mr Farrell also said the coldest and most calculated lie was the one he told gardaí about not knowing how seriously Dean Fitzpatrick was injured. He said this was to cover up the most shameful part of his actions.
"He knew he was terribly and possibly fatally injured and he ran and he did not care about Dean Fitzpatrick, he cared about himself.
"He knew full well he had dealt this blow...he wasn't going to expose himself any further by making a 999 call that would interfere with his plans to get away.
"You might think it was crazy to throw away the knife but that is what people do. It was straight out of how to get away with murder handbook, you get rid of the weapon and you don't ring 999.
"In a moment of anger he stabbed his stepson with deadly intent and left him to die in the arms of strangers. When you look at his lies you will have no hesitation in finding him guilty of murder."
The case continues on Tuesday when closing arguments from the defence will be heard.
