Mr Justice Tony Hunt said on Monday that the tragedy of the case is that neither of the brothers would have ended up in the dock in "almost any circumstance bar something out of the blue and highly unusual like this".

He said the two acted under the "misconceived but genuine sense" that they were under threat from Mr Diaconu and by their actions, they had taken his life and "blighted" their own.

Mr Justice Hunt imposed a sentence of seven years and six months with the final 18 months suspended for the rest of the defendants' lives. Should either brother be convicted of an indictable offence at any time, they may be required to serve the 18-month sentence, the judge said.

The brothers, from Castle Park, Tallaght, Dublin 24, previously pleaded not guilty to murder but guilty to the manslaughter of Mr Diaconu at their Tallaght home on December 11, 2023. The Director of Public Prosecutions accepted their pleas.

The court was told that the admission to manslaughter was accepted on the grounds that both men took part, although Eric Farrell told gardaí that only he stabbed the victim and that his brother did not harm him.

Mr Justice Hunt said CCTV from a nearby shop prior to the killing showed the twins and Mr Diaconu were being "amicable" towards one another as they purchased food, alcohol, and cigarettes before returning to the family home.

There was nothing to suggest that what happened next was a "feature of anybody's contemplation", he said.

The fatal incident "clearly flared up out of the clear blue sky, but once it flared up it did so to a very significant extent".

Mr Justice Hunt identified the aggravating factors in the case as the level of violence, the number of wounds suffered by the deceased, and the use of knives and a hammer. 

The mitigating factors included their youth, their genuine remorse, lack of previous convictions, and evidence that they were in employment and lived pro-social lives up to this offence.

Eric Farrell, said the judge, made a 999 call, attempted to do CPR on the victim, made immediate admissions, and co-operated with gardaí.

The judge noted that Sean Farrell "may have played a lesser role in the infliction of injuries", but they are equally culpable because they acted on a joint enterprise basis.

Mr Justice Hunt said both men had received favourable probation reports and are considered at a low risk of reoffending.

He set a headline sentence of ten years but, having considered the mitigating factors, reduced it to seven years and six months with the final 18 months suspended "in perpetuity".

Deceased was in relationship with twins' mother

At a previous hearing, Detective Garda Seamus Palmer, of the Special Detective Unit, told prosecution senior counsel Dean Kelly that the deceased had been in a relationship with Tanya Farrell, the defendants' mother, for some months prior to his death.

Over the last few days of his life, there were allegations of abuse or mistreatment in the relationship. During that time, gardaí were called to the house at Castle Park and arrested Mr Diaconu following reports that he had been acting aggressively towards Ms Farrell and others.

Ms Farrell went to stay with a relative and on the Monday evening, the twins went to Castle Park to speak to Mr Diaconu. At 8.36pm, Eric Farrell called emergency services saying that someone had been stabbed.

When gardaí arrived about 14 minutes later, they noticed that Sean Farrell was in a "hysterical state" and his distinctive jacket with coloured lapels was covered in blood, as were his head, hands, and face.

Eric Farrell also had blood on his hands, face and clothes and was visibly upset, crying, and sobbing. 

The deceased was lying in a pool of blood in the living room, surrounded by planks of wood, tools, and a hammer. The detective said Mr Diaconu had been putting in new floors before he died. Paramedics attempted CPR but he was pronounced dead a short time later.

A garda who spoke to Eric Farrell at the scene said he seemed "very distressed". He said he had stabbed the deceased because he had grabbed Sean Farrell during a dispute relating to their mother.

Eric Farrell admitted to stabbing Mr Diaconu, saying: "I done it, I fucking done it. I ruined it for both of us. I don't know how many times I stabbed him, I just done it." 

He asked if Mr Diaconu was OK and added: "Some Christmas this is going to be."

Sean Farrell told a garda at the scene that he and Eric Farrell had gone to Castle Park to "make sure everything was all right". He said the deceased "went for me first" with a hammer and he denied ever touching Mr Diaconu.

However, as gardaí conducted their inquiries, a neighbour told them he had been passing the Farrell home at about 8.30pm that night and saw a person wearing the same distinctive hoodie worn by Sean Farrell through the living room window, crouching down and making striking motions on the floor with his right hand.

The detective said gardaí then decided to arrest Sean Farrell, but nothing of evidential value emerged from his interviews and he made no comment when asked to account for the blood on his hoodie.

Fatal stab wound

State Pathologist Dr Linda Mulligan found eight stab wounds on Mr Diaconu's chest, neck, arms, and legs. She said the fatal stab wound was to the middle of the chest. It tracked to a depth of 20cm and penetrated the thick bones in the chest before embedding in the vertebra. It severed the aorta, causing catastrophic blood loss and rapid but not immediate death.

The other stab wounds, she said, would have bled profusely and contributed to death. She said a blunt injury to the front of the scalp could have been caused by a hammer that was found at the scene or a similar object.

Eric Farrell, in his interviews, told gardaí that he and Sean Farrell went to Castle Park because Mr Diaconu wanted a meeting to "get things back to normal". He also wanted to know where their mother was.

He said he was making pizza when "the shit hit the fan". He described coming into the living room with the pizza and seeing Mr Diaconu moving towards Sean Farrell and taking a knife from his pocket in a way that made him scared for his brother.

Eric Farrell said he picked up one knife and struck out, before taking a second knife and striking out again. He said he didn't stop until Mr Diaconu dropped his knife and fell to the floor.

He denied that his brother had ever attacked Mr Diaconu and said he couldn't understand why the neighbour said he saw a person wearing Sean Farrell's distinctive hoodie striking towards the floor.

He also said he did not remember using the hammer to strike Mr Diaconu but insisted that he had caused all the injuries to the deceased. He explained the blood on his brother's hoodie, saying the deceased was "on Sean when I stabbed him".

Det Garda Palmer said he didn't "take at face value" that Eric Farrell's description of how he used the knife was actually how it was used. He also said the forensic evidence suggested three knives had been used, not two.

Mr Kelly, prosecuting, said the manslaughter plea was accepted on the grounds that both men took part in an armed attack believing their actions were necessary to defend themselves or others but the level of violence used was objectively not proportionate.

He said the level of violence and the use of weapons put the offending into the higher culpability for manslaughter, attracting a headline sentence of 10-15 years.