A man diagnosed with paranoid schizophrenia ten years after a jury found him guilty of murdering his infant son has had his conviction quashed by the Court of Appeal.

Yusuf Ali Abdi, with a last address at The Elms, College Road, Clane, Co Kildare, stood trial in 2003 for the murder of his son, Nathan Baraka Andrew Ali, in an apartment at that address on 17 April 2001.

Abdi’s defence at trial was that he was insane and a number of medical experts were called by the defence to support that view.

He claimed he was a zombie and that voices told him to hit the child, so he struck his son against a wall several times, by swinging the child by the legs.

The prosecution also called a number of medical witnesses to say he was not psychotic.

Crucially, the prosecution called Dr Damien Mohan of the Central Mental Hospital, who said Abdi was not suffering from psychosis.

The jury rejected Abdi's insanity defence and found him guilty of murder by a 10-2 majority jury verdict. He was accordingly given the mandatory life sentence by Mr Justice Paul Carney on 28 May 2003.

However, his conviction was quashed by the Court of Appeal on the basis that a 2013 diagnosis of paranoid schizophrenia - by another psychiatrist based at the Central Mental Hospital - was new evidence, rendering his conviction unsafe.

He was remanded him in custody to appear before the Central Criminal Court on Monday for the purpose of a retrial.

Giving judgment in the three-judge court, Mr Justice John Edwards said the case was "wholly exceptional" given the change in Abdi’s diagnosis by doctors treating him at the State’s only dedicated forensic psychiatric facility in 2013.

Up until that point, a diagnosis of schizophrenia had not been made by any psychiatrist providing in-patient care for him, the court heard.

Mr Justice Edwards said time had moved on since the trial in 2003 and there had been further opportunity to observe Abdi’s condition.

It was a matter of record that Abdi’s mental ill-health was of long standing, that he remained mentally unwell, that he continued to experience paranoia and other symptoms associated with psychosis, that he was hospitalised in the CMH on multiple occasions since the trial and that doctors treating him at the CMH "changed his diagnosis".

Moreover, Abdi’s treating doctors "now regard his earlier diagnosis made at the same hospital as having been incorrect".

If the new evidence was available at the time of Abdi’s trial, it had the potential, at least, to influence the outcome, the judge said.

Mr Justice Edwards, who sat with President of the Court of Appeal Mr Justice George Birmingham and Mr Justice Patrick McCarthy, said the court felt justified in concluding that Abdi’s conviction was unsafe.

Counsel for the Director of Public Prosecutions, Jonathan Kilfeather SC, said the 2013 diagnosis was an opinion as opposed to a fact.

They argued that allowing Abdi’s appeal would open the floodgates and trials should not be reopened simply due to the passage of time.

Counsel for Abdi, Barry White SC, instructed by MacGuill and Company Solicitors, submitted that Abdi was suffering from paranoid schizophrenia both at the time of the killing and at the time of the trial.

It was not suggested that those who provided the "incorrect diagnoses" were negligent, dishonest, incompetent or acting in bad faith.

"Merely they were wrong and that subsequent events have established that they were wrong," counsel submitted.

Mr White said his client came from Somalia to Ireland in 1997 and was granted refugee status in 2000. He married Irish woman Amanda Bailey and they had a son.

At trial, Abdi gave evidence of having encountered difficulties during the war in Somalia in 1990.

He gave evidence that he saw faces and heard sounds and voices, mostly of the people who had persecuted him.

In support of his contention that the 2013 diagnosis was a new or newly discovered fact, Mr White detailed a review of material related to Abdi’s experience in detention since his son’s death, which was carried out by Dr Aggrey Washington Burke, a London-based consultant psychiatrist.

The records reviewed by Dr Burke indicated that on discharge from the CMH in June 2003, to begin serving his life sentence, Abdi’s diagnosis was depression with no sustained evidence of psychosis.

On a second admission to the CMH in September 2005, a senior medic was of the view that there was more clinical evidence of Post Traumatic Stress Disorder than of any psychotic psychiatric disorder.

In 2007, Abdi was again in the CMH for four months following his assault on a prison officer.

He complained of low mood and of hearing voices commanding him to hurt others. He was observed banging his head against the wall.

On that occasion, the senior medic believed Abdi’s complaints were not supported by observations consistent with a psychotic illness.

However, a final diagnoses in October 2013, after almost five months in the CMH, were paranoid schizophrenia and antisocial personality disorder.

Dr Burke noted that Abdi had presented with long-standing delusions involving prison officers and psychiatric staff.

He described thought interference from supernatural forces and an extensive persecutory belief system which appeared delusional in nature.

A decision was taken to stop his medication, and it was felt his mental state deteriorated. When his medication was recommenced his mood seemed to improve.

Dr Burke further noted that since Abdi’s first admission to hospital in 2001, he has consistently received anti-psychotic medication.

Since he was diagnosed with schizophrenia in 2013, he has received increased doses of the said medication with great effect and has not been involved in violent attacks on staff in prison or in hospital.

In light of the diagnosis in 2013, it was submitted that Dr Mohan’s diagnosis, though bona fide, was "erroneous" and amounted to a new or newly discovered fact.