Ten years before he became a cable news regular, Michael Avenatti joined forces with a rainmaking Los Angeles trial lawyer who had two new clients with a promising prospective lawsuit.

Brian Panish had worked with Avenatti before, and he knew him as a tough fighter capable of helping secure the millions of dollars William Parrish and Timothy Fitzgibbons felt they were due from a former employer who'd wrongfully sued them and lost.

Now, long after Panish and Avenatti took decisively different paths—one is suing Alec Baldwin over the "Rust" shooting and one is in prison—the men's business dealings are taking center stage in an Orange County Superior Court branch courthouse, where a jury is to decide whether their former clients owe their former co-counsel Robert Stoll for a $5.4 million attorney fee he never received.

The underlying case was a malicious prosecution lawsuit that settled in 2011 for $39 million—reported on Panish's website as the largest such settlement in California history.

Panish touts the settlement on his website, and Avenatti's New York public defenders mentioned it in their sentencing memorandum last week when describing Avenatti's accomplishments as a lawyer.

Neither mentions the ensuing lawsuit, but jurors were introduced to both Panish and Avenatti last week by way of photos displayed during defense lawyer Larry Conlan's opening statement in a trial nearly 11 years in the making.

Avenatti won't be testifying after invoking his Fifth Amendment right against self-incrimination. And Judge Walter Schwarm determined Avenatti's no longer a party to the case after failing to respond to pleadings. But Panish will be a key witness, with Conlan describing how he asked Avenatti to help with the case because "he thought, as he should at the time, that Mr. Avenatti would be honest with his clients."

"He's the kind of attorney who, if he's on the case, defendants start to get really worried, and they often settle cases before the case goes to trial," Conlan said, calling Panish "one of the most renowned lawyers in the country."

"And he knows what the lawyers did in the case and what the lawyers did not do in the case," continued Conlan, a partner at Cappello & Noël in Santa Barbara. "His testimony is going to help tie the whole story together."

Stoll's lawyer, H. James Keathley of Keathley & Keathley in Irvine, will begin calling witnesses June 1 at the West Justice Center branch courthouse in Westminister, nearly two months after the judge officially declared the trial underway.

Appointed to the bench in 2009, Schwarm then spent weeks navigating pretrial issues that included an unusual debate over the admissibility of a video deposition Avenatti sat for in 2015.