New Jersey Gov. Chris Christie was told about politically motivated traffic jams near the George Washington Bridge while they were crippling a town whose mayor refused to back his re-election, a U.S. prosecutor said for the first time since the scandal became public.

The assertion came on the first day of the trial of Bridget Anne Kelly and Bill Baroni, who are accused of deliberately shutting access lanes to the bridge to paralyze traffic in Fort Lee, N.J., over several mornings during the first week of school in September 2013. Prosecutors say the goal was to retaliate against Mayor Mark Sokolich, a Democrat who refused to cross party lines to back the Republican Christie.

A former Port Authority official, David Wildstein, pleaded guilty and is expected to testify that he conspired with Kelly and Baroni to punish Sokolich and cover up their crimes until the scheme came to light weeks later. In his opening statement, a prosecutor said on Monday that Wildstein and Baroni spoke to the governor on the third day of the traffic jams during a Sept. 11 memorial at the World Trade Center in New York.

โ€œDuring those precious few minutes, they bragged about the fact that there were traffic problems in Fort Lee and that Mayor Sokolich was not getting his calls returned,โ€ Assistant U.S. Attorney Vikas Khanna told jurors in federal court in Newark, N.J.

Christie has denied he knew anything of the traffic plot until weeks after it happened. Spokesman Jeremy Rosen declined to comment on Monday, citing the governorโ€™s earlier statements that he didnโ€™t know about the lane closings at the time. Wildsteinโ€™s attorney had previously said โ€œevidence existsโ€ that Christie knew about the lane closings when they occurred.

While Christieโ€™s political opponents have investigated the closings, and he commissioned a probe that cleared him of wrongdoing, this marked the first time a prosecutor publicly endorsed Wildsteinโ€™s view that Christie knew of the plot as it was happening.

Kelly, Christieโ€™s former deputy chief of staff, and Baroni, the former deputy executive director at the Port Authority of New York & New Jersey, have pleaded not guilty and promise a defense that will shed light on the inner workings of Christieโ€™s administration.

In their opening statements, lawyers for Baroni and Kelly derided Wildstein, 54, as a serial liar, a lifelong manipulator and a political operative who was Christieโ€™s enforcer to help him in his quest for the White House. They said Wildstein will lie to the jury about Kelly and Baroni to try to please prosecutors and avoid prison when heโ€™s sentenced.

โ€œDavid Wildstein is a vicious guyโ€ who was Christieโ€™s โ€œfixer,โ€ Baroniโ€™s lawyer Michael Baldassare told the jury. โ€œHeโ€™s a bully,โ€ Baldassare said before resorting to profanities to describe him.

Baldassare also revealed that Baroni worked secretly as a Federal Bureau of Investigation informant from 2006 to 2010, helping the agency investigate political corruption by lawmakers and the governorโ€™s office in Trenton, N.J. He served as a state senator during that period and โ€œcontributed in some small way to get convictionsโ€ in one or two cases, his lawyer said.

Kellyโ€™s attorney Michael Critchley said Wildstein instilled fear and intimidation throughout the Port Authority, deciding who would get fired and who would keep their job.

โ€œThis is not a situation of distant friends,โ€ Critchley said of Wildstein and Christie. โ€œThey were interacting on a very close level.โ€

Critchley said Wildstein was one of six members of Christieโ€™s inner circle as the governor pursued his unsuccessful campaign for the Republican presidential nomination.

โ€œHe said he had one constituent โ€” Chris Christie,โ€ Critchley said. โ€œHe said it was his objective to use the assets of the Port Authority to advance Chris Christieโ€™s ambitions.โ€

When Wildstein spoke, โ€œGov. Chris Christieโ€™s voice came out and everybody knew it,โ€ Baldassare said.

As recently as Sunday, Christie said he didnโ€™t know anything about the lane closings until later and would be willing to testify at the trial if called to do so.