The jury in the trial of a 21-year-old apprentice butcher accused of murdering his sister will begin considering its verdict on Monday morning.
Patrick O'Dwyer, from Shrohill, Ennistymon, Co Clare, has pleaded not guilty to murdering 17-year-old Marguerite O'Dwyer at their family home on 29 November, 2004.
The jury of six men and six women will have to decide whether he is guilty of murder, or guilty of manslaughter on the grounds of diminished responsibility.
The defence case is that Mr O'Dwyer was suffering from a mental disorder which his diminished his responsibility for the killing of his sister.
The prosecution says he is not suffering from a mental disorder.
Mr Justice Paul Carney has finished his charge to the jury members but he told them he would give them the issue paper on which they will record their verdict on Monday morning.
In his closing speech, prosecuting counsel John Edwards said one would have to be made of stone not to feel for Mr and Mrs O'Dwyer, who were sitting beside their son.
Every minute of every day, he said, they must be trying to find an explanation.
But he said an attempt to put a square peg in a round hole, even if it is done for the most compassionate reasons is 'not right, if it's not right'.
Defence counsel Patrick Gageby said this was not a common or usual case as suggested by the Director of the Central Mental Hospital, Dr Harry Kennedy.
Mr Gageby said the case had many extraordinary aspects to it. He said there was no rational, thought out motive for the killing.
And he said a decision by Mr O'Dwyer to kill his sister Marguerite because she might stop him from committing suicide was flawed and was not the product of a person 'in the fullness of his mind'.
Mr Gageby said he had never heard of anyone trying to commit suicide by hitting himself on the head with a hammer. He said it was a very complex and unusual thing to kill, for no good reason, someone you love.
He told the jury the correct verdict was not guilty of murder but guilty of manslaughter by reason of diminished responsibility.