Prosecutors maintain that their probe was well underway by the time Chadwick started his investigation in 2011. What's more, they say, the U.S. Attorney's Office took steps to ensure the Traffic Court case remained unaffected by Chadwick's findings.
As the matter finally received an airing before U.S. District Judge Robert F. Kelly on Thursday, answers remained elusive. But the unusual hearing - in which the case's lead prosecutor and one of its chief defendants took turns on the witness stand - shed new light on how the criminal case and Chadwick's report coalesced.
"The issue is whether the Chadwick investigation tainted the federal investigation," said Henry E. Hockeimer, a lawyer for Judge Michael J. Sullivan.
The FBI's 2011 raid on Traffic Court's offices near Eighth and Spring Garden Streets left the state's judiciary feeling compelled to respond, Jessica Davis, one of Chadwick's investigators, testified Thursday.
Judge Gary S. Glazer, whom Castille appointed to clean up the court, brought in Chadwick to evaluate its culture amid allegations of ticket-fixing for the politically connected.
From the start, Davis said, she and her team worked with the understanding that they and federal prosecutors would keep their inquiries separate.
Glazer sent notices to court staff requiring their cooperation with Chadwick. When it came to his fellow judges, he hand-delivered letters urging them to cooperate.
Former Judge Michael Lowry testified Thursday that the letters said the report would remain confidential and was separate from the criminal investigation.
Lowry met with Chadwick's team and outlined an extensive practice among judges of granting special consideration to certain tickets.
"This was coming directly from Chief Justice Castille," Lowry told the court Thursday. "I didn't see any other option but to cooperate. I figured the best way to keep my job was to go in there and tell the truth."
Some of Lowry's colleagues did not share his concerns. Sullivan, along with former Judges Bernice DeAngelis and Thomasine Tynes, refused to be interviewed.
Sullivan and Tynes were later indicted with Lowry on conspiracy, wire fraud and mail fraud charges.
Kevin O'Donnell, Lowry's former personal assistant, suggested that the Chadwick report might have tainted the federal case in another way.
He testified twice before the grand jury that heard the criminal case - once before the release of the Chadwick report and once afterward.
On his second stint on the witness stand, he outlined a 2009 incident in which his boss sought the dismissal of a traffic ticket given to his nephew - a detail, he testified Thursday, he had forgotten until reading Lowry's description of it in Chadwick's report.
Kelly issued no finding on the impact of Chadwick's investigation. He is expected to rule before the trial begins May 19.