A mother was convicted Monday of capital murder in the beating death of her 2-year-old daughter during a daylong discipline session in which the toddler was whipped with belts and flung across a room like a rag doll.

A jury deliberated less than two hours before convicting 20-year-old Kimberly Dawn Trenor in the death of Riley Ann Sawyers. Trenor did not seem to show any emotion after the verdict was read. The conviction brought an automatic sentence of life in prison without parole.

Prosecutors did not seek the death penalty. Jurors could have also convicted her of two lesser charges.

"Justice has been served today. Today it's about Riley. We were in that courtroom for Riley," Galveston County District Attorney Kurt Sistrunk said after the verdict.

Trenor and her husband, Royce Clyde Zeigler II, were accused of killing the toddler during the July 2007 discipline session designed to teach her proper manners. Prosecutors said Trenor and Zeigler beat Riley with belts, dunked her head in cold bath water and threw her onto a tile floor, fracturing her skull and causing her death. Zeigler, also charged with capital murder, is being tried later and remains jailed.

After Riley's death, the couple 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.

Investigators with the Galveston County Sheriff's Department dubbed the toddler "Baby Grace" during the weeks they worked to identify her remains, discovered by a fisherman on a small island in the bay.

Many of those investigators were in the courtroom Monday and they cried as the verdict was read.

"We all made a promise to that little girl ... that we would find the people responsible for her death and bring them to justice and we did," said Galveston County Sheriff's Sgt. Michael Barry, who right after the verdict was read left the courtroom and raised his fist in victory.

Trenor's defense attorney, Tommie Stickler Jr., said he was disappointed by the verdict but wasn't surprised by how quickly the jury came back with its decision.

During his closing arguments earlier Monday, Stickler implored jurors not to make a decision based on emotion but on the evidence in the case.

"I'm not going to say the jury did or didn't put away their emotions," he said. "I don't think anybody could have put them aside."

The jury foreman, Randall Rothschild, said jurors came back with a verdict fairly quickly because they felt the case was "pretty cut and dried."

"It's an emotional trial because of the victim," Rothschild said as his eyes became teary. "That was hard to set aside (emotions) and stick to the facts. But we did and justice is served."

Riley's identity was a mystery for weeks until her 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.

Sawyers testified during the trial and was in the courtroom as the verdict was read. She did not speak with reporters afterward.

"For Sheryl it's difficult. She looked at Kimberly as a daughter," said Laura DePledge, an attorney for the Sawyers family. "It's a victory for Riley but it's another loss for Sheryl and the Trenor family."

During closing arguments Monday, Sistrunk repeatedly slammed his fist against a table, telling jurors that was the sound Riley's skull made when her head was slammed against the tile floor.

Prosecutors called Trenor a cold-blooded liar who ignored her daughter's pleas to stop the abuse.

Trenor admitted taking part in the discipline session but blamed 25-year-old Zeigler for throwing Riley across the family room and causing the skull fractures.

"This was unacceptable abuse that will be punished but it's not capital murder," Stickler said during his closing arguments.

Stickler said Trenor never intended to kill her daughter and painted a picture of a frightened 18 year old at the time of Riley's death who was being controlled by her husband.

But prosecutor Kayla Allen told jurors Trenor was a strong person who killed her daughter because the girl was in the way of her happiness with her new husband.

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

Earlier Monday, Trenor's attorney presented only one defense witness, a co-worker of her husband's. The witness testified he believed Zeigler seemed to be controlling of his wife.

That followed an unsuccessful attempt by Stickler to get Zeigler to testify. Zeigler invoked his Fifth Amendment right not to incriminate himself when questioned by Stickler outside the presence of the jury.

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

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

Click here for photos of 'Baby Grace.'

Click here for photos from the trial.