Kevin Payne, 55, was the former chief of staff in the Cuyahoga County Engineer's Office.
He told the Investigator Tom Meyer exclusively in June, 2009 that he was guilty of corruption and planned to plead guilty and testify for the government.
Meyer spoke with Payne a month ago at his home in Brecksville while he was seriously ill and undergoing hospice care.
Payne told Meyer that he wasn't giving any thought to the corruption case and was concentrating on trying to feel better.
Payne was one of the first public officials to plead guilty in the case and was prepared to offer testimony against Dimora.
Prosecutors had planned to take his video deposition early next month.
Mike Tobin, spokesman for the U.S. Attorney's Office in Cleveland, said Payne's death is tragic and we extend our condolences to his family.
"His death is not going to affect the cases and we're confident we can prove the charges without his assistance, " Tobin said.