Two psychiatric experts have told the Central Criminal Court that Lynn Gibbs was suffering from a major depressive disorder on the night she killed her daughter.
Mrs Gibbs, 47, a consultant psychiatrist from Killure in Gowran, Co Kilkenny, is on trial for the murder of her daughter Ciara in November 2006.
The jury is being urged to return a verdict of not guilty by reason of insanity.
Today the court was told that Mrs Gibbs, who admits the killing, drowned her 16-year-old daughter by pushing her head into a bath full of water.
The jury of nine women and three men were told that she was worried about her daughter's anorexia and decided in a state of hopelessness that it would be best for both of them to die.
On Saturday 25 November 2006 Mrs Gibbs and her daughter went to Dublin. Ciara Gibbs attended a maths course in UCD and afterwards they both went shopping before returning home.
Ciara's father and brother had gone to visit her grandmother in Tipperary overnight.
When they returned the following morning, they found Ciara lying on the floor of an en suite bathroom while Mrs Gibbs was lying on the bedroom floor. Both were wearing their nightclothes. A meat cleaver was also found in the bathroom.
Mr Gibbs tried to resuscitate his daughter, but could not.
Mrs Gibbs told gardaí two months later that she remembered running a bath and calling Ciara. She also recalled pushing her daughter under the water.
Mrs Gibbs then took an overdose of antidepressants and sleeping tablets. She got under the water herself but could not stay under. She said she remembered being very low.
The court heard Mr and Mrs Gibbs had been concerned about Ciara's weight loss and believed she was suffering from anorexia.
Mrs Gibbs had suffered from anorexia as a teenager and had also suffered from clinical depression.
In emotional evidence, Mr Gibbs told the court his wife and daughter had a very good relationship and said that his wife loved Ciara.
The court was told the psychiatric evidence in the case was all one way and both prosecution and defence agreed Mrs Gibbs was suffering from a mental disorder, that she did not know what she was doing when she killed Ciara was wrong, and that she could not stop herself from doing it.
Mrs Gibbs has been in the Central Mental Hospital for most of the time since the killing and the court was told it is expected she will return there after this trial for further treatment.
