A WOMAN may have wanted revenge for her husband's infidelity when she killed their two young children using rat poison, a Sydney court has been told.
The mother, from Canley Heights in Sydney's west, was suffering from "major depression'' when she poisoned her children on February 19 last year.

The woman, who cannot be named for legal reasons, has pleaded not guilty to the two murders by reason of mental illness.

As her judge-alone trial began in the New South Wales Supreme Court today, the woman's lawyer told Justice Clifton Hoeben the mother didn't think life was worth living after learning about her husband's affair.

She believed she was acting in her children's best interests by killing them, the court was told.

Forensic psychiatrist Rosalie Wilcox, for the Crown prosecution, said major depression was not an often-used mental illness defence.

"She wasn't psychotic, she did have the capacity to judge the difference between right and wrong,'' Dr Wilcox told the court.

The woman was pathologically jealous and it was possible she was acting out her revenge in an attempt to hurt her husband who was planning to leave her, she said.

"Is it possible her motive was revenge and anger because she had formed the view that he was having an affair and planned to leave her?'' Crown prosecutor Margaret Cunneen asked.

"Yes, (it is possible) the event was precipitated by the accused coming to that conclusion,'' Dr Wilcox responded.

"She was considerably angry the night before. From her account she destroyed the wedding photos and had not slept very well that night. And in the morning she made a plan to take her life and the lives of her children.

"There was a degree of planning. She purchased the rat poison one morning but did not go through with it until the next day.

"I question whether there was a degree of malice in her behaviour. If she killed her children, her husband would suffer.''

Dr Wilcox said she also questioned whether the woman had really tried to take her own life that day.

"If she really wanted to kill herself, she could have done it a lot more effectively than how she did,'' she said.

The trial continues.

http://www.news.com.au/story/0,27574...-29277,00.html