A federal judge on Wednesday said the law firm retained by Gov. Christie's office in the George Washington Bridge lane-closure case engaged in "opacity and gamesmanship" while conducting a taxpayer-funded investigation into the matter.

But U.S. District Judge Susan D. Wigenton nevertheless ruled that Gibson, Dunn & Crutcher L.L.P. did not have to turn over documents requested by two former Christie allies accused in the case, because the documents either did not exist or were not pertinent to the charges they faced.

Bridget Anne Kelly, Christie's former deputy chief of staff, and Bill Baroni, a former Christie appointee at the Port Authority of New York and New Jersey, had subpoenaed notes, transcripts, and recordings of witness interviews conducted by the law firm during its representation of the governor's office.

Prosecutors say Kelly and Baroni conspired to close lanes at the bridge in September 2013 to punish a Democratic mayor because he did not endorse Christie's reelection bid that year. They have pleaded not guilty, and their trial is scheduled for April.

Christie's office hired Gibson Dunn in January 2014 after emails surfaced linking the lane closures to aides of the governor.

Gibson Dunn interviewed more than 70 witnesses and reviewed 250,000 documents during its two-month investigation. The firm issued a report saying Christie, a Republican now running for president, had no role in the lane closures.

Gibson Dunn provided interview summaries to federal prosecutors and a legislative committee investigating the lane closures.

Replying to the defendants' subpoena, Gibson Dunn said no additional notes or transcripts existed. Rather, Gibson Dunn wrote in court documents, "interviews were summarized electronically by one attorney while the interviews were being conducted and then edited electronically into a single, final version."

Wigenton, an appointee of President George W. Bush, wrote Wednesday that although Gibson Dunn "did not delete or shred documents, the process of overwriting their interview notes and drafts of the summaries had the same effect."

"This was a clever tactic," Wigenton wrote, "but when public investigations are involved, straightforward lawyering is superior to calculated strategy. The taxpayers of the state of New Jersey paid" Gibson Dunn "millions of dollars to conduct a transparent and thorough investigation. What they got instead was opacity and gamesmanship. They deserve better."

Despite Wigenton's "distaste" for Gibson Dunn's "tactics," the judge said she had no basis to doubt the firm's statements, made under penalty of perjury, that additional documents responsive to Kelly and Baroni's subpoena did not exist.

Gibson Dunn has billed taxpayers $8 million.

Kelly and Baroni also requested so-called metadata for Gibson Dunn's interview summaries, in order to identify which lawyers created or edited them. Such information, they argued, would be useful to resolve potential disputes at trial.

The defense had said that some witnesses had disputed Gibson Dunn's summaries of their interviews. Wigenton said the metadata had nothing to do with the charges Kelly and Baroni face, adding that they could call Gibson Dunn attorneys to testify at trial.