The mental status of my client will be the issue, which means entering a not guilty plea by reason of insanity

George Parnham Defence attorney

George Parnham, attorney for 36-year-old Andrea Yates, said he had seen his client over the weekend at the Harris County jail where she has been held since the murders last Wednesday.

But he said he had been unable to have a rational conversation with her.

Mr Parnham said he was studying Mrs Yates' medical history before deciding whether to proceed with a not guilty plea on grounds of insanity.

Looked after

The lawyer said his client was being looked after very well in jail by a team of mental health professionals.

He said she was "heavily medicated" but he hoped that "eventually the medication she is on will kick in and there will be some ability to have a rational conversation with her. That moment in time has not yet arrived."

The children were killed one by one

Mr Parnham said he had spoken to psychiatrists treating Mrs Yates in jail as part of his preparations for her defence.

"I've accumulated evidence in the last 24 hours that strongly suggests that the mental status of my client will be the issue, which means entering a not guilty plea by reason of insanity," he told a local newspaper.

Prosecutors have charged Mrs Yates with murder but have yet to decide whether to demand the death penalty.

Emotional pledge

An account of the killings given by Andrea Yates to police investigators was published by the Houston Chronicle newspaper last week.

Russell Yates: "She loved these kids"

It told how Mrs Yates drowned four of the children before chasing the last one, a seven-year-old son, through the house, and subsequently killing him.

Her husband, Russell, has made an emotional pledge to help his wife through the ordeal, blaming her actions on the effects of severe depression.

She was reportedly diagnosed as suffering from severe post-natal depression, and had also attempted suicide.