Was she a bad mother, or was she suffering mental illness? Jurors in the retrial of Andrea Yates are getting two different pictures of the woman charged with drowning her children in a bathtub.

In opening arguments, prosecutor Kaylynn Williford told jurors Yates knew what she was doing, and had even contemplated it for about two years. She says Yates thought she was a bad mother and killed the children so she would be punished.

Not so, says the defense. In his opening argument, Yates' lawyer says she was suffering severe postpartum psychosis, and that the condition prevented her from knowing her action was wrong.

Yates is again pleading not guilty by reason of insanity. If convicted she'll get life behind bars, because prosecutors can't seek the death penalty again without new evidence.

Since her 2002 conviction, which was overturned on appeal, other Texas juries have decided similar cases and found the accused mothers not guilty by reason of insanity.

"More people know it's a brain disorder and not just something you can snap out of," said Betsy Schwartz, director of the Mental Health Association of Greater Houston. "We can only hope the jury will have a keen awareness of the chemistry and physiology of what was going on in Andrea Yates' brain when this happened."

A prosecutor in the case said the jury must consider only the evidence presented in this case — not get caught up in public sentiment or try to send a message about mental health issues.

"This is not cookie-cutter justice," Williford said. "I believe in the insanity defense, in which someone can commit a crime and not be held criminally responsible. I do not see that in this case based on the evidence."

Yates' retrial was to begin Monday with opening statements. As in her first trial, she has pleaded not guilty by reason of insanity. If the jury agrees, she could be committed to a state hospital, with periodic hearings to determine whether she should be released. A guilty verdict would mean life in prison.

Prosecutors say they will again call Dr. Park Dietz, the psychiatrist who testified that Yates knew her actions were wrong. Dietz, also a consultant to the "Law & Order" television series, told jurors that one episode depicting a woman who drowned her kids in a bathtub — and was acquitted by reason of insanity — aired before the Yates children died.

Attorneys learned after Yates was convicted — but before jurors sentenced her to life in prison — that no such episode existed. That mistake caused an appeals court in Houston last year to overturn Yates' conviction.

Prosecutors say Yates planned the murders during the small window of time when she'd be home alone with the youngsters on June 20, 2001, after her husband went to work and before her mother-in-law arrived. Then she called her husband and 911 and later confessed, prosecutors say.

Other Texas youngsters' deaths at the hands of their mothers have drawn comparisons to the Yates case.

On the day before Mother's Day in 2003, Deanna Laney bashed her three sons' heads with rocks, killing the 8- and 6-year-olds and severely injuring the 14-month-old. The woman from the Tyler area said she believed God ordered her to kill her children, and she was found not guilty by reason of insanity.

Lisa Ann Diaz drowned her 3- and 5-year-old daughters in September 2003 in the bathtub of their Plano home. Diaz, tried only in the older child's death, was found not guilty by reason of insanity.

In 2004, Dena Schlosser cut off her 10-month-old daughter's arms in the family's Plano apartment, then called 911 while a church hymn played in the background. She, too, was found not guilty by reason of insanity.

Determining whether those verdicts indicate a trend is difficult because the cases were not identical or in the same county, said Fred Moss, an associate law professor at Southern Methodist University's Dedman School of Law in Dallas.

"This part of the country in particular is very retributive in their notions of justice and think somebody has to pay for a death," Moss said.

As in her first trial, Yates is being tried only in the deaths of 6-month-old Mary, 5-year-old John and 7-year-old Noah. She was not charged in the deaths of 2-year-old Luke and 3-year-old Paul, which is not uncommon in a case involving multiple slayings.