Analysis:The law under which Lynn Gibbs was found not guilty dates only from 2006, writes Carol Coulter, Legal Affairs Editor
Lynn Gibbs is the second person to be found not guilty of murder by reason of insanity under the 2006 Criminal Law (Insanity) Act, and the third person to plead a defence under this Act successfully.
The Act became law in June 2006, and replaced a century-old law that permitted an acquittal on the grounds of insanity, but did not allow for any consideration of diminished responsibility with regard to fatal assault.
The Criminal Law (Insanity) Act provided for three levels of mental incapacity in relation to such violent crime. A person could be found unfit to be tried at all, if he or she was unable to understand the evidence, instruct a legal representative, make a proper defence or object to a juror, by reason of a mental disorder, which is defined in the Act for the first time.
If the person is fit to be tried, he or she may still plead not guilty by reason of insanity at the time of the commission of the offence. If this plea is accepted, the person will be sent by the court to a "designated centre" for detention and treatment.
A third outcome is also available under this Act, where a person is found guilty but with diminished responsibility for the act committed, where the person does not fully meet the criteria for insanity. The charge is then one of manslaughter, which can carry a life sentence, but usually carries a lesser one.
This is the verdict that was returned in June last year in the case of Patrick O'Dwyer, a trainee butcher from Shrohill, Ennistymon, Co Clare, who attacked and killed his sister while their parents were on holiday.
Evidence was given that he suffered from "depersonalisation disorder". He was convicted of manslaughter and sentenced to six years' imprisonment.
In July 2006, shortly after the new Act came into force, John Egan of Naas, Co Kildare was found not guilty of murder by reason of insanity by a jury.
He had killed a woman he had never met before, Frances Ralph, as she waited at a taxi-rank in Naas with her husband and two friends. Mr Egan, who had earlier been thrown out of a pub when he hit a woman on the head, told the director of Dundrum Central Mental Hospital, Dr Harry Kennedy, that he had returned home, but later left for the town centre with a kitchen knife. He said that as he walked by Ms Ralph she made faces and rude signs at him.