In an opinion that harshly criticizes the tactics of the police and prosecutors, an Illinois appellate court on Friday night reversed the conviction of Juan Rivera, who has spent 19 years in jail for the 1992 rape and murder of an 11-year-old baby sitter in a suburb of Chicago.

Rivera, 39 and serving a life sentence, has been convicted three times for killing the sitter, Holly Staker, based on the strength of a confession that was obtained after four days of questioning. There were no witnesses or physical evidence linking him to the crime, which occurred in Waukegan, Ill. DNA testing in 2005 excluded him as the source of semen found in Holly’s body.