HOUSTON, Texas (CNN) — The mother of Andrea Yates described her daughter Tuesday as a great mom who loved her children and "was always watching them and protecting them."

"She was a wonderful mother and a wonderful daughter," Karin Kennedy testified in the murder trial of Yates, who is accused of drowning her five children in the bathtub of her Houston-area home.

Yates wept through much of the seven-minute testimony.

Calling Yates "my baby daughter," Kennedy said Yates graduated as valedictorian from her high school in Houston. She told the jurors her daughter cared for her children.

"She was always watching them and protecting them," Kennedy said.

Asked by the defense if the person who killed her five children was the "Andrea you knew as a loving mother," Kennedy said, "No."

The prosecution did not ask her any questions.

Earlier, prosecutors challenged a defense expert's testimony that Yates' psychiatric problems were so severe she did not know right from wrong when she drowned her five children.

Dr. Phillip Resnick, a professor of psychiatry at Case Western University, testified for the defense Friday that Yates, 37, suffered from a combination of schizophrenia, depression and other mood disorders.

In cross-examination, prosecutor Joe Owmby questioned Resnick's testimony that Yates' mental condition created "a cruel dilemma which turned upside down her sense of right and wrong," and made her believe that killing her children would save them from hell.

"Even in the face of this cruel dilemma, she knew it was a sin?" Owmby asked.

"Yes, she did," Resnick replied.

Yates has pleaded not guilty by reason of insanity, and her attorneys must prove that she did not know right from wrong for the insanity defense to be successful.

Yates is being tried on two counts of capital murder, one covering the deaths of Noah, 7, and John, 5, and the other covering the death of Mary, 6 months. She is not on trial for the drownings of Luke, 3, and Paul, 2.