Andrea Yates considered stabbing her five children but decided it was too bloody and that drowning was a better way to end their lives, a psychiatrist testified Monday.

Dr. Melissa Ferguson also said that Yates ruled out drugs to kill her children, but believed drugs were possible for suicide. Ferguson interviewed the Houston mother in jail the day after her children were drowned in their bathtub June 20.

"Do you remember her making a statement, 'After thinking about my options, I decided drowning would be the best way to end their life'?" prosecutor Kaylynn Williford said in cross-examining the defense witness.

Yates said "something about drowning, that drowning was the way," Ferguson replied. Asked by Williford if she recalled Yates saying, "I decided a knife was too bloody," Ferguson said yes.

Ferguson testified Yates told her she thought about killing her children for at least three months and thought about it the night before the children were drowned.

Yates' attorneys contend the former nurse turned stay-at-home mother is innocent by reason of insanity.

Ferguson, elaborating on her earlier testimony when she described how Yates believed she had been marked by Satan, added that Yates told her killing her children was the right thing to do.

"She was convinced that the children were going to be tormented for the rest of their lives and that they were going to perish in the fires of hell," the psychiatrist said.

Dr. George Ringholz, a neuropsychologist, also testified Tuesday that Yates told him she felt Satan's presence shortly after the birth of her eldest son, Noah.

"She heard Satan's voice tell her to pick up the knife and stab the child," Ringholz testified, adding Yates' comments were typical of schizophrenia.

Ringholz said Yates had suffered from schizophrenia since childhood and that her condition was aggravated by the birth of Noah, and again by the birth of another son in 1999.

Outside the jury's presence, Ringholz told prosecutors he was prepared to testify Yates was insane when she drowned her children.

John Bayliss, a jail nurse, told jurors Monday that Yates requested her hair be cut in the shape of a crown the day after the deaths.

Bayliss said Yates thought she may have been hearing voices in the weeks after she was jailed: "She was a person who wasn't connected with reality at all."

Yates' demeanor in jail has improved dramatically over the last few months since she's been taking medication, he said.

Other testimony this week is expected to include doctors who treated Yates before the killings.

Yates is on trial for two counts of capital murder for the deaths of three of her five children. Prosecutors are seeking the death penalty in the deaths of 7-year-old Noah, 5-year-old John and 6-month-old Mary. Charges could eventually be filed in the deaths of Paul, 3, and Luke, 2.

Prosecutors had finished their case Friday after four days of testimony from police officers, homicide detectives, a crime scene specialist and the 911 operator who took Yates' call.

Prosecutors presented an audiotaped statement Yates made to police. In it she detailed how she waited until her husband left for work to fill the tub. Jurors also viewed photos of the children's bodies.

In Texas, a person is presumed sane, and it is up to the defense to prove a defendant is insane.

Yates' medical records from 1999 detail two suicide attempts following Luke's birth and a doctor's warning that she should think twice before having additional children.

They also include a mention that Yates had her first homicidal thought following Noah's birth. If jurors determine Yates was insane, a separate hearing will be held to determine if she will be released or involuntarily committed.