Clinton Don Simpson, 76, was taken from Tarrant County Jail in Fort Worth to a hospital where he died just after 3 a.m. from blunt force injuries, the Dallas Morning News reported.
Simpson, of the small Dallas suburb of Keller, was facing charges of aggravated sexual assault of a child, continuous sexual abuse of a child under 14, and indecency by fondling.
He was placed under house arrest in 2007 and was sent to a hospital two years later to determine whether he was fit to stand trial.
He was later sent to jail and was awaiting another evaluation after being declared competent to stand trial, the paper reported.
Flores, of Fort Worth, was being held in the jail after being charged with injury to a child, elderly or disabled person stemming from an Oct. 7 incident.