A federal grand jury investigating Donald Trump’s former attorney Sidney Powell has uncovered evidence that Powell filed false incorporation papers with the state of Texas for a non-profit she heads, Defending the Republic, according to sources close to the investigation.

In the incorporation papers, Powell – who filed lawsuits across the US questioning the 2020 election result which Trump lost to Joe Biden – listed two men whom she said served with her on the organization’s board of directors, even though neither one of them gave Powell permission to do so.

As a private attorney, Powell, in the service of Trump, has gained notoriety as she has increasingly embraced implausible conspiracy theories such as that the FBI had attempted to frame Trump to drive him from office, and that Joe Biden’s election as president of the United States was illegitimate. Her lawsuits to overturn the outcome of the 2020 presidential election have all failed, often met with scathing criticism from judges who have overseen them, one of whom sanctioned her for alleged ethical misconduct and referred her to the Texas state bar for investigation.

Powell did not respond to multiple requests for comment for this story.

The broader federal criminal inquiry into Powell, led by the United States attorney for the District of Columbia, has since last fall been examining allegations of fundraising and financial fraud by Powell in the running of the group, according to documents reviewed by the Guardian.

Incorporation papers Powell filed with the Texas secretary of state on 1 December 2020 for Defending the Republic (DTR), listed only three people as comprising the group’s initial board: Powell herself, the Georgia attorney Linn Wood; and Brannon Castleberry, a Beverly Hills-based businessman and consultant.

The federal grand jury has reviewed extensive documentation that neither Wood nor Castleberry ever consented to serve on DTR’s board. One of the two men has said he wasn’t notified, even after the fact, that Powell had named him as a board member. The grand jury is investigating whether Powell misrepresented the makeup of her board in an effort to attract more donors.

The federal investigators are also trying to determine whether Powell diverted money from DTR for her own personal use.

They are also looking into whether Powell defrauded donors by falsely claiming their donations to DTR were used to finance lawsuits Powell filed to overturn the results of the 2020 presidential election. Powell has said the mission of DTR has been to “protect the integrity of elections in the United States”, but to do so required that “millions of dollars must be raised”. But investigators have only found a single instance in which DTR funds were used to finance one of Powell’s numerous high-profile election cases.

In testimony given in a civil defamation lawsuit, Brandon Johnson, an attorney for DTR, confirmed that Wood and Castleberry were listed in the non-profit’s Texas incorporation records as the group’s only other two original board members besides Powell.

During a sworn deposition in the case, Johnson testified: “That’s an important area to clarify. Apparently, the paperwork was corrected. Neither Brannon Castleberry nor Linn Wood served as directors. This was subsequently corrected.” Johnson further testified that neither Wood nor Castleberry had ever served DTR in any other capacity.

Johnson’s testimony was given in a defamation lawsuit brought against Powell by Eric Coomer, a former Dominion Voting Systems employee, against whom Powell made baseless and since throroughly debunked allegations, claiming that Coomer had conspired with antifa, the amorphous and leaderless anti-fascist movement, to steal the 2020 presidential election from Trump.

Ironically, the federal investigation is also looking into whether Powell improperly used funds from DTR to defend herself in defamation cases brought against her by both Coomer and Dominion.

Powell’s misrepresentations regarding her board are strikingly similar to other incidents during that same period.

The Guardian disclosed on Thursday that Powell had also named several individuals as plaintiffs or co-counsel in her election-related cases without their permission. Several said that they only found out that Powell had named them once the cases were already filed.

During this same time-span, Powell also named several other lawyers – albeit, with their permission in those instances – as co-counsel in her election-related cases, despite the fact that they played little or no role in bringing or litigating those cases.

A former consultant to DTR told the Guardian that Powell’s actions in lying about who was on her board, who were co-counsel or plaintiffs in her cases, and also exaggerating the nominal role of others assisting her, was to convey the appearance to potential donors that she was at the helm of an “elite strike force” who would overturn the results of the 2020 presidential election.