Williamson Co. cold case unit looks for girl’s killer 20 years later

Williamson County

WILLIAMSON COUNTY, Texas (KXAN) — The dedicated cold case unit at the Williamson County Sheriff’s Office is still searching for whoever killed a teenage girl 20 years after her death.

A rancher came across Sonya Wallace’s badly beaten, decomposing body in a creek by his property in the eastern part of the county on March 14, 1999. Wallace disappeared a month earlier after telling her family that she was walking to the post office near their home in Rockdale. 

Deputy Rex Miller, who began volunteering with the cold case unit in 2017, now serves as the lead detective into Wallace’s unsolved murder. 

“The family just really appreciates it because it gives them the feeling that someone other than them actually cares what happened to their loved one, in this case, a daughter who was 15,” Miller said. 

The case takes up much of Miller’s free time now since he retired after years working in law enforcement for a federal contractor and the Los Angeles County Sheriff’s Office. 

Even though it’s been two decades since Wallace’s death, Miller suspects that she likely knew her killer, which is a concern her parents shared at the time of her death. 

“We believe when she left the house, she said she was going to either get a stamp or mail a letter. We believe she was going to meet someone, and most of her family believes that, too,” Miller said. 

“Could she have been picked up by a total stranger? If she did, we’ll probably never solve that one, but that’s highly unlikely.” 

He said the cold case unit is doing more extensive DNA testing on Sonya’s clothing and other items collected at the scene.

He also put together a list of 300 people who may know what happened to her. 

“She was in high school: young girl in high school, very sociable, family, friends,” Miller said. “All of these people know people, and every time we talk to somebody, they give us names that we’ve never heard before that we now have to add to the list to go talk to.”

The sheriff’s office receives new tips related to Wallace’s case almost every week, and Miller said he personally follows up on each one. They may not lead anywhere, but he’s still driven by a sense of justice for Wallace and her family. 

“Is there a chance I’ll never solve it? Yes, there is, but all I can do is try.” 

Anyone who has information about Wallace’s disappearance and death should contact the Williamson County Sheriff’s Office cold case unit by either calling 512-943-5204 or sending an email to coldcasetips@wilco.org. 

This case is also being featured in Dateline NBC’s Cold Case Spotlight, where you can hear from Wallace’s mother and her suspicions about who may be responsible.   

The cold case unit is currently looking into 14 unsolved murders that date back to 1979. 

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