Former Virginia Governor Robert F. McDonnell and his wife want separate trials on the federal corruption charges they both are facing, saying in court filings late Tuesday that a joint proceeding would prevent Maureen McDonnell, in particular, from taking the witness stand to exonerate her husband.

The filings — which came on the same day that the couple’s attorneys asked a judge to toss the charges against them outright — suggest that Maureen McDonnell is willing to testify that her husband was largely in the dark about her interactions with Richmond businessman Jonnie R. Williams Sr., and that the couple could not have engaged in a conspiracy to lend the prestige of the governor’s office to Williams’s struggling dietary supplement company, Star Scientific.

Prosecutors alleged such a conspiracy in January, when the McDonnells were charged in a 14-count indictment that accused them of receiving gifts and loans from Williams totaling at least $165,000. In exchange, prosecutors alleged, Robert McDonnell hosted a product launch for Star’s dietary supplement, Anatabloc; promoted it at public events; arranged meetings between Williams and senior state health officials; and worked with his wife to encourage state researchers to consider conducting trials of the product.

The McDonnells have pleaded not guilty and a trial is scheduled to begin in July.

Drawn up by Robert McDonnell’s attorneys and endorsed by those representing his wife, the filings Tuesday posit Maureen McDonnell as the linchpin of prosecutors’ case against the couple, saying the “vast majority” of the allegations center around her relationship with Williams.

But the filings also cast her, if the cases are severed, as the possible centerpiece of her husband’s defense. Though she would invoke her Fifth Amendment right not to testify at a joint trial, the filings say, Maureen McDonnell would likely take the witness stand at an individual trial for her husband and testify that he “had no timely knowledge of many of her interactions with Williams.”

To be sure, the effort to sever the cases does not mean Maureen McDonnell is admitting wrongdoing or indicating a willingness to take a fall for her husband. Maureen McDonnell, attorneys argued in the filings Tuesday, is “not a public official, and cannot be held criminally liable in her own right for public corruption.” Prosecutors must prove she either masqueraded as a public official or worked in concert with her husband. The case, in some respects, rises and falls with the former governor.

Maureen McDonnell’s own attorneys on Tuesday moved to throw out the corruption charges on those grounds, arguing that she was still a private citizen as the governor’s wife and should not be charged with public corruption related offenses. They also moved to toss an obstruction of justice charge their client is facing alone, saying she had no knowledge of any federal investigation or any intent to hinder it when the alleged misdeed occurred.

The motion to sever, though, was far more interesting, opening a window into the couple’s marriage and offering a preview of the possible trial — or trials — to come.

Defense attorneys wrote that Maureen McDonnell’s relationship with her husband was “strained,” in part because of the former governor’s demanding work and travel schedule, and that she and her husband did not act “in concert” when it came to Williams. They said the indictment had alleged only in “conclusory terms the existence of a conspiracy between the McDonnells. But it provides no specific allegation of an agreement between them.”

“Instead, the Government appears to be inferring a conspiracy solely by virtue of their marriage,” defense attorneys wrote.

Defense attorneys wrote that if the trials were severed, Maureen McDonnell would likely waive her Fifth Amendment right not to testify and dispute prosecutors’ central allegations. Separate trials, they argued, would also allow Robert McDonnell to talk freely about his and his wife’s private conversations because Maureen McDonnell would not invoke marital privilege to prevent her husband’s testimony.

Robert McDonnell would dispute many of prosecutors’ allegations about a conspiracy between him, his wife and Williams, if he were not prevented from doing so by his wife’s invoking marital privilege, the attorneys wrote.

Prosecutors had yet to respond to — and a judge had yet to rule on — the filings very early Wednesday morning. Defense attorneys asked that the legal proceedings be severed as soon as possible.