Attorneys for a mother accused of beating to death her 2-year-old daughter during a daylong discipline session rested their case Monday after presenting only one witness at her capital murder trial.

The jury of seven women and five men was expected to begin deliberating Kimberly Dawn Trenor's fate after closing arguments Monday afternoon.

Trenor's only defense witness, a co-worker of her husband's, testified he believed Royce Clyde Zeigler II seemed to be controlling of his wife. Trenor's attorneys have argued to jurors that Trenor was under Zeigler's control and she was not responsible for the death of toddler Riley Ann Sawyers.

Scott Estes also told jurors he overheard Zeigler at work speaking angrily to his wife on the phone, and that he saw Trenor act depressed during a company picnic that occurred after Riley's death. Last week, another co-worker testified the couple was playful at the same picnic.

Trenor and Zeigler are accused of killing Riley during a July 2007 discipline session designed to teach her proper manners. Prosecutors say they beat her, dunked her head in cold bath water and threw her onto a tile floor, fracturing her skull and causing her death.

The couple then stuffed her body in a plastic box and hid it in a storage shed at their suburban Houston home before dumping it in Galveston Bay, according to authorities. Both are charged with capital murder; Zeigler will be tried later. The girl became known as "Baby Grace" while investigators worked to identify her body.

Trenor could receive an automatic sentence of life in prison without parole if convicted of capital murder. The jury could also convict her of a lesser charge. She already has pleaded guilty to tampering with evidence.

The defense's only witness followed an unsuccessful attempt by Trenor's defense attorney, Tommie Stickler Jr., to get Zeigler to testify at his wife's trial.

Outside the presence of the jury, Stickler asked Zeigler three questions: whether he had stated in a suicide note his wife was innocent; whether he had told police he was asleep during the attack; and if he told a relative that police thought he was just like his father, who family members have said hit his wives.

But each time, Zeigler invoked his Fifth Amendment right not to incriminate himself.

State District Judge David Garner ended the questioning, saying that it was obvious Zeigler wouldn't answer any questions.

Galveston County Medical Examiner Stephen Pustilnik, the final prosecution witness, testified Monday that any reasonable person could have seen Riley had been affected by having her head hit the floor and was in need of medical attention.

In a videotaped statement to police, Trenor admitted taking part in the discipline session but blamed Zeigler for throwing Riley across the family room and causing the skull fractures.

Documents shown to jurors indicated Zeigler wrote a suicide note absolving Trenor in Riley's death. But after his arrest, Zeigler wrote a letter in which he said his wife was lying. Zeigler's family members told jurors last week they grew wary of excuses the couple gave for Riley's absence and ultimately confronted them about their suspicions.

Trenor and Zeigler met playing an online video game and married in 2007 after Trenor moved with her daughter from Mentor, Ohio, a suburb of Cleveland, to Spring, a suburb north of Houston.

The toddler's identity was a mystery for weeks until Riley's paternal grandmother in Ohio, Sheryl Sawyers, saw an artist's sketch of the girl and told authorities in Texas she thought it was her granddaughter.

The call from Sheryl Sawyers led authorities to Zeigler and Trenor, who had invented a story that Riley had been taken away by child welfare officials in Ohio.

Prosecutors declined to seek the death penalty against either her or Zeigler, 25, because they didn't think they could prove that the pair would be a future danger, a requirement for such a punishment.

Trenor and Zeigler are being held in the Galveston County Jail under bonds of $850,000 each.

Click here for photos of 'Baby Grace.'

Click here for photos from the trial.