Updated

Andrea Yates' five children died slowly, each struggling and gasping for air as she drowned them one by one in the family bathtub, a pediatric pathologist testified Saturday.

It would have taken each child three minutes to lose consciousness, and another three minutes to die, the pathologist said. In each case, he said, Yates would have had time to resuscitate the child afterward but didn't.

"Each of these children did not want to die, and they fought their deaths," Dr. Harry Wilson, a pathologist at Texas Tech University School of Medicine, said during the third week of testimony in Yates' capital murder trial.

Yates, 37, has pleaded innocent by reason of insanity.

Tears rolled down her face Saturday as she listened to Wilson describe her children's fight for life.

Testifying for the prosecution, Wilson described the bruises on the children's bodies and used a life-sized infant doll to show how Yates pushed the forehead of her youngest child, 6-month-old Mary, against the bottom of the bathtub.

He said autopsies found bacteria in the children's lungs which showed they had inhaled vomit- and feces-riddled water in the tub as they were being drowned.

Harris County Sheriff's deputy Mike Stephens testified that he overheard Yates tell a jail psychiatrist that she was stupid for not just killing her 6-month-old daughter.

Stephens said he overheard Yates tell Dr. Melissa Ferguson during an interview at the jail that she knew her actions were wrong as she held each of her five children beneath the water's surface.

During cross-examination, defense attorney George Parnham asked Stephens if he eavesdropped on a private conversation between Yates and Ferguson.

Stephens said no, "I just stood there and listened," eliciting laughs from spectators.

On Friday, forensic psychiatrist Dr. Park Dietz, who interviewed Yates in November, testified that Yates had thought about killing her children before and had let other opportunities pass because she "wasn't ready."

When asked during the videotaped interview how she got ready, Yates replied: "Just mentally, to do it."

"I needed to go ahead and do it," she said.

On June 20, after her husband left for work, Yates drowned all five children in the bathtub, then called police and confessed. Officers found Noah, 7, face down in the bathtub, and the bodies of John, 5, Paul, 3, Luke, 2, and Mary under a wet sheet on a bed.

Yates is being tried on only two counts of capital murder and could face other charges in the future.

To prove insanity and spare Yates from life in prison or the death penalty, defense attorneys must show she suffered from a severe mental disease or defect and didn't know her actions were wrong at the time of the killings.

She has been diagnosed with schizophrenia by both defense and prosecution experts. Before the drowning, she had been treated for postpartum depression.

Defense attorneys are trying to prove that Yates was in a delusional and psychotic state and thought that drowning her children was the only way to save them from eternal damnation.