NEWARK — Gov. Chris Christie of New Jersey was told about the George Washington Bridge lane closings — and that they were done to punish a mayor who had declined to endorse him for re-election — during a Sept. 11 memorial service two days after they began, a former ally who orchestrated the scheme testified in federal court here on Tuesday.

Mr. Christie, the witness recalled, laughed at the news.

The closings of the access lanes in September 2013 continued for two more days, creating a catastrophic traffic jam that created gridlock for emergency vehicles, school buses and commuters in Fort Lee, N.J.

But Mr. Christie made no effort to reopen the lanes and end the gridlock.

Instead, his former ally said, the governor was clearly delighted and seemed to savor the scheme. And after learning that the Fort Lee mayor’s persistent and urgent calls for help were being ignored, Mr. Christie said in a sarcastic tone, “I imagine he wouldn’t get his calls returned.”

The former ally, David Wildstein, who has pleaded guilty to being the culprit behind the lane closings, testified as prosecutors showed a series of photographs of him, Mr. Christie and Bill Baroni, then the governor’s top staff appointee at the Port Authority of New York and New Jersey, which runs the bridge, at a service in Lower Manhattan on the 12th anniversary of the Sept. 11, 2001, terrorist attacks.