Murder accused was suffering from cannabis-induced psychosis, psychiatrist tells trial

Murder Accused Was Suffering From Cannabis-Induced Psychosis, Psychiatrist Tells Trial
Diego Costa Silva (right) has pleaded not guilty to the murder of Fabiola De Campos Silva (left) on November 4th, 2021.
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Eoin Reynolds

A man killed and decapitated his wife while suffering from a cannabis-induced psychosis that led him to believe she was possessed by a serpent and was going to kill him, two consultant psychiatrists have told the Central Criminal Court.

One of the psychiatrists said the accused man, Diego Costa Silva, believed that after attacking his wife, Fabiola Camara De Campos Silva, he had to remove her head to make sure that the serpent was dead.


Both psychiatrists agreed that Mr Costa Silva's psychosis was not due to acute intoxication from cannabis, but a more persistent illness of cannabis induced psychosis. The court heard the accused continued to display psychotic symptoms 11 days after his arrest and detention.

Dr Brenda Wright and Dr Mark Joynt told the trial that cannabis induced psychosis is a mental disorder under the Criminal Law (Insanity) Act 2006.

They agreed that, as a result of his disorder, Mr Costa Silva did not understand the nature and quality of his actions and did not know that what he was doing was wrong.

Counsel for the defence and prosecution also delivered their closing speeches to the jury on Thursday, saying the evidence shows that, due to a mental disorder, Mr Costa Silva is not responsible for his actions and should be found not guilty by reason of insanity.


Mr Costa Silva (35) has pleaded not guilty to the murder of Ms De Campos Silva (33) on November 4th, 2021, at their home in Charlestown Place, Finglas, Dublin 11.


Dr Joynt was called by the defence and told Garnet Orange SC, for Mr Costa Silva, that he interviewed the accused three times, spoke to his sister in Brazil and read the book of evidence and other documents.

He said Mr Costa Silva's sister told him that a number of members of their family had been diagnosed with bipolar disorder.

Dr Joynt said this family history puts Mr Costa Silva at a higher risk of developing a serious mental disorder, including substance induced psychosis.


He noted that two days prior to killing his wife, Mr Costa Silva had been taken to the Mater Hospital by gardaí who had a concern for his mental health. Doctors at the Mater asked Mr Costa Silva to remain as a voluntary patient, but he refused and left on November 3rd.

The notes taken by doctors at that time suggest that Mr Costa Silva was suffering symptoms of psychosis including confusion, thought disorder and a paranoid belief that his wife would hurt him.

Ms De Campos Silva was recorded to have told doctors that she noted a sudden change in her husband's behaviour the previous Saturday, but she said he had not smoked cannabis for several days.

In his interviews with Dr Joynt, Mr Costa Silva said he had begun smoking cannabis at 16 and from the age of 20 would smoke daily. In 2020, he said his wife told him he was smoking too much, and he agreed to cut down.


He did not think he had smoked cannabis in the days immediately prior to killing his wife, the court heard.

Dr Joynt said that in the lead-up to killing his wife, Mr Costa Silva said he was convinced that she wanted to kill him and that he could hear voices external to his head.

He came to believe that his parents were being held by a gang and that his wife was possessed by the leader of the gang, in the form of a serpent.

He believed he was going to die and that he had to kill his wife to defend himself, the doctor said. After he attacked his wife, Mr Costa Silva believed "the serpent wasn't dead, and he had to cut the head off to make sure it was dead".


Following his arrest and detention, Mr Costa Silva continued to show psychotic symptoms until November 15th, 11 days after the killing. Two days after that, when Mr Costa Silva had spent five days taking the antipsychotic drug Olanzapine, he was reported to be improving and to have gained insight into his illness and what had happened.

Mental disorder

When Dr Joynt last spoke to Mr Costa Silva in November last year, he said he found no evidence of active psychotic symptoms. He said this was one of the reasons he did not diagnose the accused with a more persistent illness such as schizophrenia.

This is not intoxication, this is a mental disorder.

Dr Joynt concluded that Mr Costa Silva was suffering from a cannabis induced psychotic disorder, the symptoms of which included hallucinations and delusions regarding his wife.

He said that he excluded intoxication as a diagnosis because the symptoms persisted for 11 days after the killing, a period in which Mr Costa Silva did not have access to drugs. He said this would not be consistent with the effects of acute intoxication from cannabis, which typically wears off within hours.

In conclusion, Dr Joynt said that due to his mental disorder, Mr Costa Silver did not know the nature and quality of his actions, did not know that what he was doing was wrong and was unable to refrain from his actions.

Dr Brenda Wright told Shane Costelloe SC, for the Director of Public Prosecutions, that she agreed with most of Dr Joynt's conclusions.

The only significant distinction, she said, was that she believed he could have refrained from his actions by avoiding his wife, as he had done previously when suffering similar delusions.

In his closing speech to the seven men and five women of the jury, Mr Costelloe said the prosecution had proven beyond reasonable doubt that Mr Costa Silva killed his wife and that when he cut her head off, he intended to kill her.

If the jury agrees, he asked them to consider the evidence of the psychiatrists who both said that Mr Costa Silva was suffering from a mental disorder and that he is not responsible in law for his actions.

"All of the evidence adduced points only one way," he said, "and you must act upon the evidence."

He said the jury may ask themselves how somebody can abuse illegal substances and rely on that as a defence.

However, he added: "You heard from both psychiatrists that this is not intoxication, it is not taking drugs or alcohol and then going and doing something, that would not be a defence. This is not intoxication, this is a mental disorder – cannabis induced psychosis."

Counsel described it as a "particularly horrible case" and a "deeply tragic case" in which a young woman lost her life and her husband finds himself having killed his wife with whom he had enjoyed an otherwise healthy relationship.

He asked the jury to put aside emotion, sympathy and personal feelings and view the evidence dispassionately.

If they find that Mr Costa Silva did have a mental disorder that removed his responsibility for the crime, they must return a verdict of not guilty by reason of insanity, he said.

Mr Garnet Orange, for the defence, said he agrees with everything said by counsel for the prosecution. He asked the jury to put aside any views they might have about drug use or domestic violence or any feelings of "disdain or horror" that they might ordinarily feel.

He said: "The defence is looking for a special verdict, the evidence is before you, and it does only point in one direction as far as the defence and prosecution are concerned, and you must keep that in mind... The verdict I am asking you to return is not guilty by reason of insanity."

Mr Justice Michael MacGrath has begun charging the jury, who will be asked to begin considering their verdict on Friday.

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