HOUSTON (AP) — Andrea Yates was a mere "shell," a threat to herself and her children, in the weeks before she drowned them in the bathtub, a psychiatrist testified Monday.

Ellen Allbritton, who admitted Yates to Devereux Texas Treatment Network on March 31, said she immediately recognized Yates was someone who required in-patient treatment. Yates' five children were dead less than three months later.

"When I walked in the room and saw her, I pretty much knew this was someone who needed to be in the hospital," said Allbritton, testifying for the defense as the third week of testimony in Yates' murder trial got under way. "She looked mentally ill."

Asked by defense attorney George Parnham to elaborate, Allbritton said: "Someone who had declined to the point of non-function, just there, a shell."

In her medical notes, Allbritton wrote that Yates, whose father had died about three weeks earlier, "needs in-patient stabilization for safety of self and others."

Under cross-examination, Allbritton told prosecutor Joe Owmby that Yates denied having any suicidal or homicidal thoughts but: "I wouldn't have trusted her to walk across the street."

Allbritton said Yates and her husband, Russell, were hesitant to hospitalize her and did so only after Allbritton filed an emergency detention order.

"The patient was so ill and had obviously been ill for quite some time," Allbritton said. "I really wondered why she hadn't been presented to our facility sooner."

Defense attorneys are trying to show Yates didn't know right from wrong on June 20, when she drowned her children.

Yates, 37, who has pleaded innocent by reason of insanity, faces murder charges in the drownings of 7-year-old Noah, 5-year-old John and 6-month-old Mary. Charges could be filed later in the deaths of Paul, 3, and Luke, 2. She faces life in prison or the death penalty if convicted.

An expert witness who testified for the defense last week told jurors Yates suffers from schizophrenia, which was worsened by her bouts with postpartum depression following the births of her fourth and fifth children.

Schizophrenia causes a person's thinking, feeling and behavior to become impaired. It includes symptoms such as delusions, hallucinations and social withdrawal.

Defense witness Phillip Resnick told jurors Friday that Yates knew her actions were illegal, but that she thought drowning her four sons and 6-month-old daughter was the only way to save them from hell.

Resnick is considered one of the nation's top forensic psychiatrists, having testified in the cases of serial killer Jeffery Dahmer, Unabomber Ted Kaczynski and Susan Smith, the South Carolina mother sentenced to life in prison for drowning her two sons in 1994.

Determining if Yates knew right from wrong will be a key decision for jurors in the case where there is little debate over whrzvy 4.hes drowned her children or whether she suffered from a mental illness.

To prove insanity, defense lawyers must prove Yates suffered from a severe mental disease or defect and that she didn't know her actions were wrong.