Schar made the claim while asking a judge to order Stepien and Kelly to comply with subpoenas the panel issued seeking communication records related to the September lane closures, which snarled traffic in Fort Lee over four days.
Christie fired Kelly and cut ties with Stepien in January, after the release of documents revealing Kelly had evidently sent an e-mail in August that said, "Time for some traffic problems in Fort Lee."
Stepien had referred in an e-mail to the Fort Lee mayor as "an idiot," according to the documents, which the legislative committee obtained through a subpoena issued to a former official at the Port Authority of New York and New Jersey.
The panel has since issued dozens of subpoenas, including to Kelly and Stepien. In court Tuesday, lawyers for the former Christie advisers argued their clients should not have to comply with the demands because they would violate their Fifth Amendment rights against self-incrimination.
Marino said the committee did not have enough proof to justify its demand that Stepien turn over documents.
He said the panel had presented to the court five e-mails involving Stepien. That didn't make it a "foregone conclusion," he said, that Stepien had more documents - a threshold he argued needed to be met for the subpoena to be valid.
Judge Mary C. Jacobson pressed Schar on how he knew more e-mails existed. "Is there anything in the e-mails you've shown me that suggests the existence of other documents?" she asked.
"That's a difficult question to answer," Schar said. He cited "the scope of discussion" and said, "What we have is evidence there was significant communication on this topic over e-mail."
Later, after Marino had made his argument during the three-hour hearing, Schar said the committee had received "a number of additional e-mails" involving Kelly or Stepien. He did not describe their content.
"I don't need to guess, judge," Schar said. "The answer is: We were right. There are additional documents."
In the letter and court filing Wednesday, Marino demanded that the committee provide the documents within five days.
Assemblyman John S. Wisniewski (D., Middlesex) and Sen. Loretta Weinberg (D., Bergen), the committee cochairs, did not indicate Wednesday whether they would provide documents.
"We'll review Mr. Marino's letter, but continue to urge Mr. Stepien to do the right thing and comply with the subpoena and provide documents that could shed light on the abuse of government power and threat to public safety that surrounded the decision to restrict access lanes to the George Washington Bridge," they said in a statement.
Under an order from Jacobson, the committee must provide the court an additional brief by Monday addressing whether it could enforce its subpoenas through contempt power, and whether it could grant immunity to defendants in exchange for producing documents.
Kelly and Stepien will have until March 24 to respond.