The Lake County coroner's office on Sunday identified the man who died after being found unresponsive in his county jail cell last week as 36-year-old David Butterfield of Zion.
The coroner's office said preliminary findings of an autopsy indicate Butterfield died of natural causes attributable to advanced peritonitis, an inflammation of the thin tissue that lines the inner wall of the abdomen. There were no signs of internal or external trauma to Butterfield's body, and toxicology results are pending, the coroner's office said.
Butterfield was found unresponsive in his medical unit jail cell Friday, according to the Lake County sheriff's office. Jail medical personnel immediately began administering aid, and he was later taken to Vista East Hospital in Waukegan, where he was pronounced dead, officials said.
Authorities said the Lake County Major Crime Task Force is investigating, as part of a recently established protocol by the sheriff's office.
Butterfield was brought to the jail Monday, Feb. 29, after being arrested on a warrant for failing to appear in court on a drug charge, authorities said.
While in custody, he reported feeling ill from drug withdrawal symptoms and was put under the care of the jail's medical unit, the sheriff's office said.