HOUSTON -- A couple accused of beating their toddler to death, tucking her body in a plastic box and dumping it in Galveston Bay were indicted Wednesday on charges of capital murder.

Galveston County District Attorney Kurt Sistrunk said he had yet to decide whether to seek the death penalty against Kimberly Dawn Trenor and her husband, Royce Clyde Zeigler II, in the death of Trenor's 2-year-old daughter, Riley Ann Sawyers.

The grand jury also charged Trenor and Zeigler with tampering with evidence, a second-degree felony punishable by two to 20 years in prison.

The couple was charged in November with tampering with evidence and injury to a child. DNA tests have since proven the body belonged to Riley, allowing the charges to be upgraded.

Trenor, 19, told authorities that she and her 24-year-old husband beat and tortured Riley to death in July in a discipline session that veered out of control. She said they hid the girl's body in a shed for two months before dumping it in the bay.

The box containing the body washed ashore and was found by a fisherman in October. Authorities dubbed Riley "Baby Grace" as they spent weeks searching for her identity and family.

Attorneys for the pair did not immediately return telephone calls seeking comment. Both lawyers said earlier this week that they did not believe the facts of the case merit a capital charge.

An attorney for the toddler's father, Robert Sawyers, and paternal grandmother, Sheryl Sawyers, told The Galveston County Daily News this week that the family has reservations about Trenor facing the death penalty. If Trenor is convicted of capital murder, the only other sentence she could receive is life in prison without parole.

According to Trenor's attorney, Tommy Stickler Jr., Zeigler wanted Trenor to spank Riley with a belt when she failed to say things like "please" and "yes sir" or "no sir." Zeigler didn't believe Trenor was doing it, however, because the 2-year-old's behavior wasn't changing.

The fatal beating happened after Zeigler stayed home from work to make sure his wife was following his discipline plan, Stickler said.

In a statement to authorities, Trenor said the girl was beaten with leather belts, had her head held underwater in a bathtub and then was thrown across a room, her head slamming into a tile floor.

An autopsy revealed that Riley suffered three skull fractures, but the cause of death has not been determined.

Zeigler's attorney has said Trenor's credibility will become an issue once all the facts are examined.

(Copyright 2007 by The Associated Press. All Rights Reserved.)