TRENTON -- Gov. Chris Christie has long maintained that he's been cleared by three separate Bridgegate investigations, including one by the U.S. Attorney for New Jersey.

Late Tuesday afternoon, former U.S. Attorney for New Jersey Paul Fishman took exception to the governor's characterization during an interview with CBS News. He said the lack of an indictment didn't mean innocence.

"We don't actually say people didn't do something, we don't say that they're innocent," Fishman told WCBS newsradio. "We bring cases when we have sufficient evidence to prove people guilty, and we don't when we don't."

Fishman's words echoed an early interview with WNYC last week. Appearing on "The Brian Lehrer Show," a caller asked Fishman why the governor had not been charged in the politically-motivated, traffic-as-revenge scandal.

"Many people believe he had a heavy hand in participating in that bridge closure," the caller told Fishman. "Did you not find anything that would prove that, or did you just decide not to bring charges against him?

Fishman's answer suggested that he thought the governor was responsible, but that there was insufficient evidence to secure a conviction.

"The one thing I will say is that sometimes, in the criminal law, there are instances in which we are able to prove that certain people are responsible, and we're not able to go further."

Last week, Christie took a swipe at Fishman's tenure saying that he hoped Fishman's recent ouster from the politically appointed office might see the office "restored to its past success."

In his Tuesday interview with WCBS, Fishman said that the Bridgegate investigation that took down three former Christie allies might be coloring the governor's estimation of his tenure there.

"I'm not sure how the governor measures success," said Fishman. His office oversaw the guilty plea of two Christie Port Authority appointees, the conviction of two top Christie allies, along with the indictment of a former Christie cabinet member who died with a federal conspiracy to commit bribery investigation pending.

"I can only assume that some of the decisions I made as United States attorney made him a little uncomfortable," Fishman said.

Earlier this month, a Bergen County judge ruled there would be no special prosecutor to handle a citizen activist's criminal complaint of official misconduct. The citizen activist, Bill Brennan, has vowed to appeal.

Claude Brodesser-Akner may be reached at cbrodesser@njadvancemedia.com. Follow him on Twitter @ClaudeBrodesser. Find NJ.com Politics on Facebook.