In the filing, federal prosecutors included portions of an Aug. 13, 2007 conversation between Carona and former assistant sheriff Don Haidl.
At the time, Haidl had already pleaded guilty to a lesser charge in the probe and was secretly cooperating with the government's investigation.
In the transcript, Haidl and Carona discuss cash and gifts Carona received from Haidl and what they would do if other witnesses testify about them to the grand jury.
They also talked about whether another assistant sheriff witnessed Haidl giving cash to Carona in July 2002, when Haidl's son was arrested, and whether federal prosecutors would be able to trace the money, according to excerpts of the transcript included in the court filing.
"Whatever we did, as long as our stories are straight, I'm okay, as long as I know there's no trail anywhere," Haidl told Carona, according to the transcript.
Carona replied, "No trail anywhere," the transcript said.
When Haidl needs further assurance, Carona added, "Period. Period. In fact, not even close to being a trail."
Carona's attorney did not immediately return a call and e-mail requesting comment.