A federal jury convicted Derrick Mosley, 39, of two counts of extortion and two counts of wire fraud for allegedly plotting to extort money from Sheffield and gospel singer DeLeon Richards-Sheffield.
Assistant U.S. Attorney Clarence Butler said Mosley asked Sheffield's business agent for $20,000 to destroy a tape that Mosley claimed showed Richards-Sheffield having sex with Kelly before she married Sheffield.
"I think what was paramount throughout this case is that Derrick Mosley was convicted by his own words," Butler said.
Defense attorney Michael Petro declined to say Monday if he had seen the purported sex tapes, citing attorney client-privilege. R. Kelly's attorney, Edward Genson, declined to comment.
Rufus Williams, Sheffield's Chicago-area business agent, alerted the FBI after Mosley first contacted him on Nov. 3, 2004. Williams later taped a conversation with Mosley.
Mosley also called the Yankees media office last November to try to contact Sheffield and told a team official about the tape, Butler said.
In a statement he gave last year, Sheffield supported his wife and acknowledged that she "had a long-term relationship with a well-known professional singer over 10 years ago," which he knew about.
Williams testified during the trial that Mosley, who describes himself as a minister, told him Richards-Sheffield "needed to atone, she needed to repent." Williams also said Mosley raised the idea of being a paid spiritual consultant.
Petro said Mosley only wanted to provide moral counsel to the couple.
"The only thing Derrick Mosley wanted was atonement from DeLeon Richards," said Petro, "There was never a threat to expose the tapes."
Mosley planned to appeal the verdict.
His sentencing was scheduled for Jan. 18. He faces a maximum of 44 years in prison, Butler said.