The CBS newsman later got a lecture from the judge for trying to interrogate a lawyer while on the witness stand.
"No, no, no, Mr. Rooney," said federal Judge Colleen McMahon, her head in her hands. "The first rule is the witness never gets to ask any questions ... even if he's a journalist."
Rooney was the first witness in the fraud trial of Alan Walker, 67, who ran the Program Corp. of America, a firm that matched speakers with events. Rooney testified Walker owes him about $10,000 from a 2003 speech at Indiana State University.
Other witnesses in the trial are former basketball star Magic Johnson, retired astronaut Scott Carpenter, and Robert Ballard, the undersea explorer who found the wreck of the Titanic.
Rooney, 86, entered the courtroom muttering, and he balked when asked to swear to tell "nothing but the truth, so help you God."
"I don't know about God," he said, taking the witness chair.
Rooney said he signed a contract with Walker for $20,000 plus expenses. "I'm not the greatest speaker in the world, but they seemed to like it," he said.
He said when he wasn't paid, he made several calls - "He was always in the Middle East or someplace" - then complained to the Better Business Bureau. He said he sent back an "unacceptable" check for $2,500.
Rooney testified he began to think the episode "might make a piece for me for '60 Minutes,"' and took a camera crew to Walker's office and home - but didn't find him.
When defense lawyer Kerry Lawrence asked Rooney how he found Walker's address, Rooney said he didn't remember, but, "As an old reporter, we have a few secrets, and the first thing is we try the phone book."
Afteward, Rooney said he got a check for $10,000.