Lawyers for Ashli Babbitt have accused the Department of Justice of providing "inconsistent" reasons for their decision not to charge the officer who shot and killed her during the Capitol riots on January 6.
Babbitt, 35, was part of the mob of Donald Trump supporters that stormed the building while Congress was preparing to certify Joe Biden as the winner of the presidential election.
Footage of the moment when Babbitt was shot was widely shared online. It showed rioters trying to break through a glass door separating a hallway from the Speaker's Lobby and Chamber.
As the crowd were attempting to smash through the door, Babbitt began climbing through a broken window. An officer inside the Speaker's Lobby fired once, striking Babbitt in the left shoulder. She later died from her injuries.
In a statement on Wednesday, the U.S. Attorney's Office in Washington, D.C. said an investigation into the shooting found "insufficient evidence" to support a criminal prosecution against the officer.
The statement said there was "no evidence to establish beyond a reasonable doubt that the officer willfully" committed an unlawful act.
It went on: "Specifically, the investigation revealed no evidence to establish that, at the time the officer fired a single shot at Ms. Babbitt, the officer did not reasonably believe that it was necessary to do so in self-defense or in defense of the members of Congress and others evacuating the House Chamber.
"Acknowledging the tragic loss of life and offering condolences to Ms. Babbitt's family, the U.S. Attorney's Office and U.S. Department of Justice have therefore closed the investigation into this matter."
In a statement seen by The Washington Examiner, Terrell Roberts, an attorney representing Babbitt's family, rejected the Department of Justice decision, accusing prosecutors of contradicting themselves in their reasoning.
Roberts pointed out that the U.S. Attorney's Office statement declared that the investigation did not establish beyond a reasonable doubt that the officer "willfully committed a violation" of Title 18 U.S. Code Section 242, but in the next sentence said it found "no evidence" the officer "did not reasonably believe" it was necessary.
The attorney said: "This double-negative is an odd way of explaining the basis for not bringing charges. It plainly glosses over the obvious problem of squaring the decision not to prosecute with the known facts.
"The actual evidence is this: the officer shot an unarmed woman who was not an immediate threat to him or any member of Congress. That is inconsistent with any claim of self-defense or the defense of others, period.
"To kill Ashli Babbitt in the way it was done demonstrates the requisite degree of willfulness to support a prosecution under the civil rights statute previously referred to."
Roberts added that he and the Babbitt family "strongly disagreed" with the decision but were not "dissuaded from our goal of ultimately vindicating Ashli Babbitt's constitutional rights in the civil arena."
John Sullivan, who filmed the moment Babbitt was shot, was later charged with a number of offenses over the events of January 6.
Roberts has been contacted for further comment.
Babbitt was one of five people who died during or shortly after the riots, including Capitol Police Officer Brian Sicknick.
The chief medical examiner of Washington D.C., Francisco Diaz, concluded that Kevin Greeson, 55, of Athens, Alabama, and Benjamin Philips, 50, of Ringtown, Pennsylvania, died of natural causes. The death of Roseanne Boyland, 34, was ruled an accidental amphetamine overdose.
Investigators have not established a cause of death for Officer Sicknick.
