"I caused his life to be lost. I wish with all my heart and soul for forgiveness but I cannot ask you for it because I can never forgive myself," Damien Singleton told the family of Peter Donnelly.
Over the course of two trials, the Donnelly family had to "repeatedly" watch the death of their loved one on CCTV evidence that went before the jury.
"No family should witness what you witnessed on CCTV," Singleton also told them.
In her victim impact statement, Mr Donnelly's mother told Singleton that she "will not allow anger into my heart or I am no better than the person who did this terrible, cowardly deed".
Quoting the author Lois McMaster Bujold, she told the Central Criminal Court: "The dead cannot cry out for justice; it is the duty of the living to do so for them."
Singleton (31) of no fixed abode, had pleaded not guilty to murder but guilty to the manslaughter of his friend Peter Donnelly (39), who was originally from Kilkenny, on O'Connell Street in Dublin on June 11, 2019.
Last month he was found unanimously guilty of the murder by 11 jurors who had viewed CCTV of the stabbing attack and who listened to a voicemail sent by Singleton threatening Mr Donnelly before the killing.
Mr Lorcan Staines SC, prosecuting, had said the stabbing was "vicious and devastating", adding that less than one hour earlier Singleton had voice-messaged Mr Donnelly saying: "I promise you, I'll slit your fucking throat. Pray I don't get you. I'm going to slaughter you. You're dead."
"That's exactly what he did. This is murder, pure and simple", said Mr Staines in his closing speech to the jury.
In her victim impact statement read out Mr Staines today, Mr Donnelly's mother, Pauline O'Keeffe, said that every day since the murder has been a struggle and that she was "paralysed by grief".
"It has been 906 days since Peter was murdered. Every morning I wake up, the first thought in my mind is that Peter is dead. I struggle to get past that thought. I struggle to get out of bed to go to work. I struggle to keep myself together. In fact, for a long time, I could not get out of bed I was so paralysed by grief.
"A huge part of our lives, Peter, is missing - taken so barbarically, cruelly, without a chance to say goodbye or hold his hand. It is unbearable to think about the way in which he died."
Ms O'Keeffe said: "It is now time for my words to be heard. I would like to quote the author Lois McMaster Bujold: 'The dead cannot cry out for justice; it is the duty of the living to do so for them.'
"I remember when he was small every night before I put him to bed, he would lay his head on my lap and I would rub his nose until he fell asleep. Then I would carry him up to bed and whisper, 'Night, night. I love you'. On the day I pushed Peter's coffin into the chapel and down the aisle, and the coffin was opened, I again rubbed his nose and said: 'Night, night. I love you.'
"That was the very last time I saw Peter in this life. I wait for the day I see him in the next.
"I have experienced many emotions since Peter died. Sadness, great grief, helplessness, frustration, and an emptiness that only a mother who has lost a child can feel. The one emotion I will not allow myself to feel is anger. Anger is soul destroying. Anger eats you up. I will not allow anger into my heart or I am not better than the person who did this terrible, cowardly deed.
"We will always tell him [Peter] that we love him and remember him with dignity. Peter was much loved," she said in her statement.
Singleton, who abandoned prepared notes, directly addressed the Donnelly family and said in evidence that he was "about to receive a life sentence but it won't affect me any more than what I go through when I think about taking Peter's life".
"I caused his life to be lost. I wish with all my heart and soul for forgiveness but I cannot ask you for it because I can never forgive myself. Peter was a good friend of mine, he saved my life," said Singleton.
Singleton said that Mr Donnelly had taken him to England and taught him how to make furniture but that when they arranged to meet in Dublin both men "relapsed" into drug addiction. Singleton told the family that he could not be forgiven for causing the killing of Mr Donnelly and that he was sorry for putting them through a trial. "No family should witness what you witnessed on CCTV," he said.
Singleton said that "all the sorrys in the world" would not bring back Mr Donnelly and that his life sentence was "minuscule" compared to what the family were going through.
Corina Donnelly, Peter's aunt, described her nephew as a "never a nobody, he was always a somebody". Ms Donnelly said she could always see past Mr Donnelly's addiction issues to his "charming, lovely personality", adding that he always saw the good in people. Ms Donnelly said her family and her three daughters would "never be the same".
Ms Donnelly said Peter had lectured on mental health and addiction issues and that he had treated her daughters "like sisters", creating "so many happy memories". She said she found it "hard to put into words" that the family were without Peter.
She said that she would leave forgiveness "to the man upstairs" and that she struggled to come to terms with the "brutal" manner of his death. "The last face Peter saw was that of the person who took his life," she said.
In her victim impact statement, Tracy Brennan, the mother of Mr Donnelly's youngest child said he was "so proud, so excited" to be a father again but he never got that chance as his baby boy was seven months-old at the time of his murder.
She said that their son will never have the excitement or have any photos of birthdays or communions and will miss out on "so many milestones" with his father.
"One day, I'll have to tell him why daddy is in the stars", she said, adding that she herself suffered a "horrific breakdown" in the aftermath of the killing. She said it was "difficult to see Peter" in her child's face but that she was also blessed that her son was like his father and that she would "bring up that boy to be a good man".
When sentencing Singleton to the mandatory life sentence today, Ms Justice Deirdre Murphy offered her condolences to the "dignified" Donnelly family, who had "repeatedly" watched the death of Mr Donnelly over the course of two trials.
Ms Justice Murphy said that there was a "fine thread that binds each of us to life" and that people were entitled to live it with "respect and dignity".
The trial had centred on whether or not Singleton, who was on a cocktail of drugs and alcohol at the time, was capable of forming the intent to kill Mr Donnelly, which is required for a murder conviction.
The jury rejected the defence case that Singleton was so intoxicated at the time he was incapable of either knowing what he was doing or was incapable of knowing the consequences of his actions.
It was the second trial of Singleton after the first collapsed last September. The first trial was abandoned after one of the jurors believed they overheard gardaí discussing witness statements in the courtroom.
At that hearing, prosecution counsel told the court that gardaí "absolutely did not discuss witness statements" in the courtroom but submitted that the jury should be discharged due to the impression formed by them that one of their members had overheard discussion.
The trial heard that Mr Donnelly died from stab wounds to his aorta and jugular vein in the early hours of June 11, 2019, caused by a knife that Singleton carried in his tracksuit bottoms.