Talk-show hosts call her a monster, civil-rights groups say she is sick and shouldn't stand trial. Andrea Yates, who drowned her children, is about to face a jury that will decide whether she too must die, reports Patrick Smyth, Washington Correspondent.

On a June day at her home in Houston, Texas, last year, 37-year-old Andrea Yates started to drown her five children - Mary, Luke, Paul, John and Noah - one by one in the bath. As she held six-month-old Mary under the water, her eldest, seven-year-old Noah, came into the bathroom.

"What's wrong with Mary?" he asked. Then he realised what she was doing and turned to flee. She raced after him, dragging the boy back to the bath, where she drowned him beside his sister.

Yates took the dripping bodies of her five children and laid them out in bed, as if they were asleep. Then she calmly called the police. And then her husband at work. "What's wrong?" he asked.

"You need to come home," she said.

"Anyone hurt?" he asked.

"Yes," she said.

"Who?" he asked.

"The children - all of them."

He told reporters later: "My heart just sank."

On Monday, lawyers finished selecting a jury of eight women and four men, with testimony expected to begin by the middle of next month. Seven of the jurors say they have children.

Two of the women have psychology degrees. The 12 will decide whether Yates must die too, as she has been charged with capital murder. Texas has executed 257 people since 1997, one third of the US total.

Here they execute the mentally handicapped and juvenile offenders. Here they now want to put to death a woman who, by all accounts, was suffering from acute post-natal psychosis, who had been four times confined to a psychiatric hospital for treatment in the two years before the killings.

At the time, she told doctors she had twice tried to commit suicide because voices and visions that started with the birth of her first son began telling her to get a knife and hurt someone.

Yates has pleaded not guilty by virtue of insanity, but the test of insanity is difficult. Jurors must find both that she had a severe mental disease or defect and that she did not know her actions were wrong.

In September a jury found her competent to stand trial - a different issue - and in December a judge ruled that her confession to police at the time is admissible.

The prosecution says that if she faces up to her responsibility and admits her guilt, it may not seek her death. "Even at this stage, for example, the defendant could choose to accept criminal responsibility, which would be an additional mitigating factor and would, I believe, very likely call the state to recommend a life sentence," Joe Ownby, the prosecutor, told a preliminary hearing.

The case has deeply divided the country, with women's organisations and civil-rights groups braving considerable opprobrium by arguing against her prosecution while talk-show hosts describe her as a monster.

But her husband, Rusty, is standing by her.

On television in December, in breach of a judicial gag order, he insisted that had his wife received competent psychiatric care, she wouldn't have been in the mental state that caused her to kill their young children.

"The medical community failed us," he said. "You know, the person that drowned those children is not Andrea. If your brain is sick, then you can think things that aren't real," he told 60 Minutes, the CBS news magazine programme. "I don't blame her a bit.

"If she had received the medical treatment she deserved, then the kids would be alive and well. And Andrea would be well on her way to recovery. And we'd be unknown," he said, insisting she should not have been released from hospital four weeks before the killings.

While 80 per cent of new mothers suffer from baby blues, a short-term weepiness that tends to pass quickly, post-natal depression is a more serious condition that afflicts between 5 and 20 per cent of women after they give birth.

It is characterised by persistent anxiety, hopelessness, guilt, insomnia and lack of motivation. It may occasionally give rise to fantasies about harming oneself or one's children.

Post-natal psychosis, into which Yates sank, is far less common, occurring in one to two new mothers in every 1,000. In those cases, women often become delusional and sometimes hear voices urging them to commit suicide or harm their babies.

Almost all of those who harm their children are suffering from post-natal psychosis.

The diagnosis and treatment of post-natal depression is usually quite straightforward. The condition is believed to have largely physiological causes, rooted in the wild swings in oestrogen and progesterone levels that pregnancy brings.

Other problems, such as marital stress or sleep deprivation, exacerbate the condition, but doctors are treating many women in such conditions with oestrogen patches, to ease the hormonal fall after birth.

Post-natal depression can be treated with medication and counselling; the psychosis may require mood stabilisers, such as lithium.

Women who have had post-natal depression are those most likely to get it again, as the brain appears to remember the experience of childbirth and magnifies its reaction to it.

In Yates's case, this was particularly so: the birth of Mary had plunged her into a profound depression exacerbated by the death of her father, whom she had for a long time nursed through Alzheimer's.

Two months before she drowned her children in the family bath, she was so profoundly disturbed that her husband checked her into a Houston psychiatric hospital after she filled the tub with water and refused to explain why.

She was discharged four weeks later and her doctors took her off Haldol, a powerful drug often used to control hallucinations and other psychotic symptoms.

In the US, some 200 children are killed by mothers each year, many of them suffering from post-natal psychosis. Psychologists call them altruistic killings - the mothers are usually deeply caring but suffering from a strong sense of inadequacy as mothers.

Yates told police she killed the children, whom she doted on, because she thought that she was a bad mother and that they were "hopelessly damaged". She thought they'd be better off with God. According to a report in Time magazine, she also claimed to be possessed by the devil.

Indeed, the Yateses' commitment to their children was such that she had given up her nursing job to teach them at home.

In treatment notes, therapists described a husband so eager to get her out of the hospital that he was "putting some pressure on her to leave". They also described a wife anxious to drop the medication that had begun to reverse her mental illness, so she could "get pregnant and have more children home-school them".

"Patient and husband plan to have as many babies as nature will allow!" one therapist wrote in August 1999. "This will surely guarantee further psychosis and depression."

Yates's mother, Jutta Kennedy, told Newsweek magazine: "She was the most compassionate of my children. Always thinking of other people, never herself. She always tried to care for everybody."

But Yates had few friends, no outside interests and little self-esteem. Her husband, an engineer with NASA, though caring and concerned, appears to have been controlling.

For several years she brought the family up in a mobile home. Eventually, her closed-in world became too much.

Initially, she has been charged with only three of the five deaths, a standard practice in multiple-murder cases, which allows the prosecution the opportunity to enter further capital charges if the first case, for some reason, falls apart.

The prosecution will rely on the shock value of the killings to insist to the jury that someone must pay, but the central focus of the trial will be a duel between experts on criminal insanity: for the state,a renowned forensic psychiatrist, Dr Park Dietz of California; for the defence, Dr Phillip Resnick, an expert on post-natal psychosis. Dietz almost always testifies for the prosecution and specialises in high-profile cases, most notably those of serial killers Jeffrey Dahmer and John Hinckley.

Police officer Frank Stumpo, the second officer on the scene, told the preliminary hearing that he asked Yates if she knew what she had done. "She looked me directly in my eyes and said, 'I know what I've done, I killed my children,' " he claimed.

One of the biggest hurdles for Yates is that juries don't like insanity defences. Jurors often believe, incorrectly, that defendants who are found not guilty by reason of insanity are freed.

Texas law, designed to make securing convictions easier, prohibits a defence lawyer from telling the jury that a finding of insanity will mean lengthy secure confinement in psychiatric care. In fact, studies show that defendants acquitted in insanity cases and sent to mental hospitals spend more time confined than if they had been sentenced to prison.

But this is Texas.