Twin brothers killed their mother’s partner after he became abusive towards her, the Central Criminal Court heard on Monday.

The court was told the admission to manslaughter by brothers Eric and Seán Farrell, 21, was accepted on the grounds they both took part, although Eric told gardaí that only he stabbed the victim and his brother did not harm him.

A barrister for Seán Farrell said the brothers ‘behave and act more like two halves of one person’ and there is ‘clearly an instinctive action and reaction in terms of protecting each other’.

Nicolae Diaconu, 45, died after suffering eight stab wounds, some as deep as 20cm, to his chest, legs and neck, and from a blunt force wound to the front of his head.

Eric and Seán Farrell, from Castle Park, Tallaght, Dublin 24 previously pleaded not guilty to murder, but guilty to the manslaughter of Mr Diaconu at their home on December 11, 2023.

The DPP accepted their pleas and Judge Tony Hunt heard evidence and mitigation at a sentencing hearing on Monday.

Detective Garda Séamus Palmer told prosecution senior counsel Dean Kelly the deceased had been in a relationship with Tanya Farrell, the defendants’ mother, 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 Castle Park and arrested Mr Diaconu after reports he acted 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 called emergency services saying someone had been stabbed.

When gardaí arrived about 14 minutes later, they noticed Seán was in a ‘hysterical state’ and his jacket was covered in blood, as were his head, hands and face. Eric 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 at the scene said he seemed ‘very distressed’. He said he had stabbed the deceased because he had grabbed Seán during a dispute relating to their mother.

Eric admitted to stabbing Mr Diaconu and added: ‘I done it, I f***ing 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 ‘okay’ and added: ‘Some Christmas this is going to be.’

Seán told a garda at the scene that he and Eric 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 and saw a person wearing the same hoodie worn by Seán through the living room window, crouching and making striking motions on the floor with his right hand.

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

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 and a blunt injury to his head could have been caused by a hammer that was found at the scene, or a similar object.

Eric, in his interviews, said he and Seán went to Castle Park as Mr Diaconu wanted to ‘get things back to normal’. He also wanted to know where their mother was.

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

Eric 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 his brother attacked Mr Diaconu, and did not remember using the hammer to strike him. He insisted he caused all the injuries and explained the blood on his brother’s hoodie, saying the deceased was ‘on Seán when I stabbed him’.

Counsel asked the court to consider this a ‘once-off’ incident, as stated by the probation services. He said both men wished to communicate their ‘deep sorrow and regret’ to Mr Diaconu’s family.

Judge Hunt remanded them in custody for sentencing on June 15.