A woman accused of holding her 4-year-old stepson in a scalding bath, covering his burns and not getting him medical care before he died was sentenced to at least 18 years in prison after pleading guilty to murder and other charges on Thursday.

A Warren County judge sentenced Anna Ritchie to 18 years to life in prison after she changed her plea from not guilty.

Ritchie was arrested after the March death of Austin Cooper. A detective said Ritchie told police that she put Austin's legs in extra-hot water as punishment because he didn't like baths and that she tried to hide his burns.

Her attorneys had tried unsuccessfully to have evidence from her interview with Franklin police detectives excluded from the case.

County Prosecutor David Fornshell alleged that Ritchie held Austin in extra-hot water for 20 to 25 minutes as he struggled, then put him to bed wearing pajamas and socks to cover his bleeding feet and burned skin, his arms cut where her fingernails had grasped him. His father found him dead in his crib more than 16 hours later, Fornshell said.