A Texas housewife on trial for bashing her three sons with rocks, killing two, is a textbook example of insanity as defined by state law, a psychiatrist testified Friday.

Psychiatrist William Reid said he could use the case of Deanna Laney (search), who said God told her to kill her children last Mother's Day weekend, to teach students about Texas' definition of insanity.

Laney has pleaded innocent by reason of insanity to charges of murdering 8-year-old Joshua and 6-year-old Luke and severely beating Aaron, then 14 months old. Prosecutors are not seeking the death penalty.

All five mental health experts consulted in the case said Laney had psychotic delusions and was incapable of knowing right from wrong at the time of the killings, the legal standard in Texas for insanity.

Reid said the case is the first time he's seen such agreement among experts in similar trials.

Prosecutors have portrayed the slayings as selfish acts, and maintained Laney had to have known she was doing wrong. Her first call was to 911 to summon authorities.

On Thursday, Laney's older sister said Laney was eating less, losing weight and reading the Bible more in the weeks before admitted killing her two older sons and severely injuring her toddler.

Pam Sepmoree was the first family member to testify that she noticed even the slightest changes in Laney before the killings.

"She was low, she was down. She didn't talk much," Sepmoree said, explaining that she believed her sister was "very sick and insane" to have killed the boys.

Sepmoree told jurors that her sister had been a devoted mother. "The boys were her life," she said.

Six days after the attacks, Laney calmly recounted the slayings and told a psychiatrist she was awaiting her children's resurrection, according to a videotape shown to the jury Thursday.

Laney's behavior was in chilling contrast to the sobbing, emotionally broken and seemingly tortured demeanor she displayed in a video made seven months later, and shown to jurors Wednesday.

In the tape made days after the killings, Laney was wide-eyed, occasionally smiling and animated as she described events leading up to the bloodshed.

"I feel like that I obeyed God and I believe there will be good out of this," she told psychiatrist Dr. Phillip Resnick. "I feel like he will reveal his power and they will be raised up. They will become alive again."

In court, Laney's husband, Keith Laney, held his head in his hands and appeared to weep after watching his wife's calm description of the violence. Keith Laney has stood by his wife.