NEWARK, N.J. (AP) — The attorney for one of New Jersey Gov. Chris Christie's former aides raised questions Friday about the credibility of the prosecution's key witness during cross-examination in the George Washington Bridge lane-closing trial.

Michael Critchley, Bridget Kelly's defense attorney, called David Wildstein a liar on Friday, describing the former Port Authority of New York and New Jersey executive as someone who would do whatever it took to further his own interests.

Kelly, Christie's onetime deputy chief of staff, is on trial with former Port Authority of New York and New Jersey executive Bill Baroni. They are facing civil rights and wire fraud charges.

Wildstein, a former executive at the Port Authority, pleaded guilty in the case and is cooperating with federal prosecutors.

Critchley noted lies that were told to senior managers at the Port Authority in 2013, when he was planning a series of unauthorized lane closures to send traffic jams into Fort Lee as political retribution against the borough's Democratic mayor who didn't support the Republican governor in his re-election bid.

Critchley asked Wildstein whether he inaccurately said the closure was a traffic study. Wildstein called it a false statement, but Critchley said it was a lie.

Critchley revisited earlier testimony from Wildstein, who admitted to playing a series of political tricks as a young Republican operative, including taking the late Democratic U.S. Den. Frank Lautenberg's jacket before a debate so he would "feel uncomfortable."

"You know what a euphemism is?" Critchley asked. "You explained it by saying you were an exuberant volunteer. That's a euphemism. You were a thief."

Wildstein said he wasn't "willing to accept that representation" and admitted he made a bad decision.

"At the time I was proud ...," Wildstein said. "I'm embarrassed by it now."

Wildstein testified Tuesday that Christie was told about the traffic jam while it was underway and seemed happy about it. Christie has repeatedly denied that and has not been charged with a crime.