Publicist Thom Serafin said Rizzo died Sunday at Northwestern Memorial Hospital, where he had been for three weeks, the Chicago Tribune reported.
For more than 25 years, both while licensed as a private investigator and while suspended, Rizzo worked divorce cases and became a regular guest on the "Phil Donahue" talk show, detailing his old-fashioned and high-tech techniques of catching people up, the newspaper said.
In the 1970s, Rizzo was convicted on federal charges of illegal eavesdropping, which cost him his private detective's license, but he continued to work, claiming he didn't need his own license as an employee of a company.
His ernierizzo.com Web site lists more than 30 high-profile and celebrity cases he worked on, and features a picture of Rizzo bare-chested on a camel, working a case in Egypt.
Rizzo is survived by his wife, Geraldine; a son and daughter.