Dr. Phillip Resnick, who evaluated Yates about three weeks after the June 2001 drownings, said she knew her actions were illegal but didn't know they were wrong because she was trying to save the children from going to hell.
"If she did not intervene and take their lives while they were still innocent, they would end up in hell," he said, testifying as a defense rebuttal witness. "Mrs. Yates knew what she was doing was right for her children."
Yates, 42, is being retried because an appeals court overturned her 2002 capital murder conviction on the grounds that some erroneous testimony may have influenced jurors. Yates, charged in only three of the children's deaths, has again pleaded not guilty by reason of insanity.
If convicted, she will be sentenced to life in prison. If found not guilty by reason of insanity, she will be committed to a state mental hospital, with periodic hearings before a judge to determine whether she should be released — although jurors are not allowed to know that.
Her attorneys say she suffered from severe postpartum psychosis and meets Texas' definition of insanity: that a severe mental illness prevents someone who is committing a crime from knowing it is wrong.
On Tuesday, jurors saw a 14-minute videotape of Resnick's interview with Yates in jail on July 14, 2001. She answered questions about the drownings after listing her children's names and ages: Noah, 7; John, 5; Paul, 3; Luke, 2; and Mary, 6 months.
"They just did a lot of silly stuff and didn't obey. When Rusty's mom would visit, they wouldn't treat her well, call her names," she said, adding that they were not developing correctly and were unrighteous. "They didn't do things God likes."
When asked how she felt about the children, she said, "I didn't hate my children." When Resnick asked whether she loved them, she responded, "Yes. Not in the right way, though."
Yates did not show remorse then because she was too psychotic and still thought that killing the children was in their best interest, he said.
But when he evaluated her four months later, he said, she had been taking anti-psychotic medication and realized she had "needlessly taken her children's lives ... so it was a very different picture."
Resnick, a psychiatry professor at Case Western Reserve University in Cleveland, began testifying after the state rested its case Tuesday.