A 36-year-old man has admitted killing freelance journalist Tom O'Gorman at his home in Castleknock in Dublin in January of last year.

Saverio Bellante, from Palermo in Sicily, pleaded not guilty to the murder of the 39-year-old at Beech Park Avenue, Castleknock, Dublin at a time unknown between 11 and 12 January 2014.

The jury was told it will have to consider if he was suffering from a mental disorder at the time and can therefore benefit from the special verdict of not guilty by reason of insanity.

Warning: This report contains graphic content which some readers may find disturbing

In his opening statement, Senior Counsel Patrick Gageby said the two men had met through an international religious group, which promotes benevolent values, such as brotherhood and unity.

Mr Bellante rented a room in Mr O'Gorman's house in Castleknock and moved into Beech Park Avenue in November 2013.

The court was told that he had been diagnosed with a mental disorder, "religious hysterical delirium", and had delusions he was Jesus Christ.

The court was told this afternoon Mr Bellante had been hospitalised in Sicily and had been prescribed anti-psychotic medication after exhibiting signs of stress by praying all day without rest.

On 11 January 2014 both men were in the house and had played a game of chess.

But Mr Gageby told the jury that a number of unusual things occurred. Mr Bellante left a message on an acquaintance's phone asking him to mediate in a dispute over chess.

He also called his sister in Italy and made references to "omerta" and "the mafia" which she took as ominous signs as she had been conscious of his previous breakdown and mental disorder.

The court was then told Mr Bellante called gardaí on 999 at 1.50am on 12 January and told them he had killed Mr O'Gorman with a dumbbell and a knife and said it had something to do with a row over chess.

Gardaí arrived and discovered the body in the sitting room beside a small table.

There was an "enormous amount of blood" the court heard, and "unusually a cutting open of the front of the chest".

Mr Gageby said it appeared part of Mr O Gorman's lung had been cut out and brought to the kitchen.

Prosecuting Counsel told the jurors they will have to decide whether or not Mr Bellante should be held responsible for the murder if he did not know what he was doing, if he did not know it was wrong, or if by reason of his illness he could not stop himself.

Defence Counsel Sean Guerin made a number of admissions on behalf of Mr Bellante including admitting that he killed Mr O'Gorman, that he was lawfully arrested, detained and interviewed and that the 39-year-old freelance journalist who also worked with the Iona Institute died from blunt force trauma and stab wounds to the neck and chest.

Mr Bellante told gardaí he killed Mr O'Gorman and then decided it was better to remove his heart.

He told them he removed it with his hands, that it was in two pieces, big and small, and that he ate the big piece but left the smaller piece on a dish in the kitchen because "it wasn't for me".

His interviews with the gardaí were read out in court today.

He also told detectives that it was necessary to kill Mr O'Gorman because he wanted to kill him - not physically but he wanted to remove his freedom.

He said people want to steal your freedom, make you a slave. He said he had not planned to eat his heart but realised at the last minute he had to do it.

He said the mafia is managed by the political heart and head.

He said normally it was wrong to kill a man but not in this specific case because he was not free to decide.

He also told the gardaí that Mr O'Gorman was fake, keen on sport and politics but he had different points of view and this was the way to trick people.

He said they were playing chess together and Mr O'Gorman was losing.

Mr Bellante said he moved the King and Mr O'Gorman got angry, said it was a stupid and perverse move and did not want to keep playing.

He said that he told Mr O'Gorman that he was playing "respecting the rules" but Mr O'Gorman did not accept that.

He said Mr O'Gorman was on the sofa, he was sitting on an armchair.

He asked Mr O'Gorman to say sorry, Mr O'Gorman said never - but then he said sorry.

He said he then asked Mr O'Gorman could he smoke in the house and he said yes "this is the only time."

He said Mr O'Gorman stared at him, that he was very scared and that he knew he wanted to kill him.

Mr Bellante was advised to gradually stop taking medication, court told 

Clinical Forensic Psychiatrist at the Central Mental Hospital, Dr Stephen Monks, told the court that a doctor told Mr Bellante to come off anti-psychotic medication gradually and that he stopped on the 9 of January.

He said Mr Bellante told him he started to feel unwell the next day, 10 of January, the day before the murder. 

Dr Monks testified that Mr Bellante's anti-psychotic medication had been reduced by slow taper.

Dr Conor O'Neill said it had been reduced in steps of 2.5mg from 20mg to 0 between July 2012 and 9 Jan 2014 and that Mr Bellante was so severely ill after the murder that he had to be immediately transferred to the Central Mental Hospital where he was a risk to others and it was necessary to restrain, seclude and nurse him in isolation from other patients.

Dr Monks said he displayed features of psychosis typical of schizophrenia, disjointed and disordered thoughts, pre-occupied with pseudo philosophical musing.

He said he diagnosed schizophrenia and delusional behaviour so that Mr Bellante believed that killing Tom O'Gorman would put an end to evil in the world.

He said Bellante was unable to reason outside his psychotic thought processes and did not know what he was doing was morally wrong.

Both he and Dr O' Neill testified that they believed Mr Bellante meets the criteria to be considered not guilty by reason of insanity.

Dr O'Neill said Mr Bellante later expressed remorse to the O'Gorman family, as well as his own family, and was sorry for what happened.

Dr Monks said Mr Bellante began to interpret things as good and evil  and told him that he was watching a football match and saw it as a battle between good and evil.

He said that after he had played the chess game on 11 January with Tom O' Gorman, he believed the 39-year-old was on the side of evil because he did not respect the rules of the game.

Two briquettes on the fire also represented good and evil to him he said and when they both became ash he was not so angry he told the psychiatrist. 

He said he got a jar of water from the kitchen and poured half on the fire handing the other half to Mr O' Gorman to resolve the fight between good and evil, but Mr O' Gorman said no.

"I decided to take the knife and kill him at that moment, I thought he was the devil", the psychiatrist said Mr Bellante told him.

The trial continues tomorrow.