The son of former Labour MEP Proinsias De Rossa has been found not guilty through insanity of assaulting his father in their Dublin home.
The jury returned the verdict following a few minutes' deliberation after being told by the judge that the appropriate verdict is not guilty under the Criminal Law Insanity Act 2010.
Fearghal De Rossa (46) severely beat his father in an unprovoked attack. A passer-by said he was sure he was trying to kill his father as he beat him with a shovel.
Mr De Rossa said he had pursued the prosecution of his son only to get him to submit to psychiatric treatment.
Judge Desmond Hogan committed Fearghal to the Central Mental Hospital for treatment.
The trial heard evidence from two psychiatrists that he suffers from a mental disorder and did not know what he was doing was wrong.
Fearghal De Rossa of Old Finglas Road, Glasnevin, had pleaded not guilty at Dublin Circuit Criminal Court to assault causing harm to his now 72-year-old father at their home on November 11, 2011.
During Mr De Rossa's trial both the prosecution and defence cases were almost identical. Both agreed that an assault took place and that Fearghal was legally insane at the time. However a trial was required because the Criminal Law Insanity Act states that only a jury can decide if the insanity defence is valid.
The trial had previously heard that Mr De Rossa Snr had just returned from the inauguration of President Michael D Higgins when the attack began.
He was in hospital for six days and required surgery to his forearm.
He said his son calmly told him, "I'm going to kill you", before starting to punch him.