With former Virginia governor Robert F. McDonnell’s trial on public corruption charges just days away, his attorneys want to subpoena materials about the alleged misdeeds of a government witness, saying they might erode her credibility and the credibility of the man for whom she worked.

The eleventh-hour legal wrangling concerns the testimony of Jerri Fulkerson, who was the longtime personal assistant of the Richmond businessman at the center of the case against McDonnell and his wife.

Prosecutors have alleged that businessman Jonnie R. Williams Sr. lavished gifts and money on McDonnell and his wife, Maureen, and that in exchange, the couple lent him and a company he once ran the prestige of the governor’s office. Among other things, the McDonnells let Williams use the governor’s mansion to launch one of his company’s products, prosecutors have alleged.

This week, prosecutors requested that Fulkerson — who was expected to be only moderately important as a witness in the trial — be given immunity for her testimony. Prosecutors did not make clear why immunity was considered necessary.

In filings Friday, defense attorneys said prosecutors told them that Fulkerson, a notary, “possibly [had] notarized signatures of Mr. Williams that were not in fact his” and that “on occasion . . . Williams instructed Fulkerson to sign [certain] documents on his behalf.” According to defense attorneys, prosecutors had requested that she be given immunity because she planned to invoke her Fifth Amendment right at trial to avoid speaking about those possibly illegal acts.

Former Virginia governor Robert F. McDonnell, accompanied by his wife, Maureen. (Steve Helber/AP)

Defense attorneys said that Fulkerson’s and Williams’s actions call into question their credibility and that the defense needed all materials stemming from the alleged misconduct to help them cross-examine both witnesses at the trial.

“Such conduct is not only a violation of her oath as a notary, but depending on how and where these forged and falsified documents were used and submitted, it could also constitute a wide array of criminal offenses, including bank fraud, securities fraud, or tax fraud,” defense attorneys wrote. “Indeed, this evidence is doubly exculpatory in that it would enable Mr. McDonnell to impeach not one but two key Government witnesses. If Mr. Williams directed and benefited from this illegal conduct, he would be equally culpable.”

If the request had come earlier it might have been resolved without much effect on the proceedings. But with 150 prospective jurors scheduled to arrive at the federal courthouse in Richmond on Monday, a resolution could be inconvenient.

Defense attorneys requested an expedited ruling from the judge on their request, noting that they would need “all the time possible to review this information and incorporate it into the cross-examinations.” They wrote that though prosecutors had interviewed Fulkerson on June 26, 2013, June 5, 2014, and July 14, 2014, they apparently did not learn of the “falsely notarized” documents until two days ago.

An attorney for Fulkerson declined to comment.

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