NEWARK, N.J. — The prosecution’s key witness is back on the stand at the George Washington Bridge lane-closing trial.

Former Port Authority executive David Wildstein faces cross-examination Tuesday. He pleaded guilty and is cooperating with prosecutors.

Before the trial broke for the Jewish new year on Monday, an attorney for one of New Jersey Gov. Chris Christie’s former aides raised questions about Wildstein’s credibility. Bridget Kelly’s attorney called Wildstein a liar.

Kelly was Christie’s deputy chief of staff. She and former Port Authority of New York and New Jersey executive Bill Baroni are facing civil rights and wire fraud charges.

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