Could a social media post by a Department of Justice official thwart Attorney General Pam Bondi’s hopes of securing a death penalty sentence for Luigi Mangione?

Lawyers for the accused UnitedHealthcare CEO killer are expected to argue exactly that in a sweeping legal filing due Friday. The motion — spanning approximately 15,000 words across 50 pages — is so extensive that the defense team had to request special permission from the court to exceed normal length limits.

The brief will include both a motion to dismiss the charges and a motion seeking to exclude from any trial certain evidence obtained at the time of Mr. Mangione’s arrest in Pennsylvania. 

Federal prosecutors sought earlier this week to convince the court that they did not violate the judge’s order to refrain from commenting publicly on the case. 

The government came under fire after a justice department spokesman, Chad Gilmartin, posted a clip on X on September 19 in which President Trump said Mr. Magione “shot someone in the back.” Mr. Gilmartin shared the clip along with the caption: “@POTUS is absolutely right.” His post was then shared by a DOJ associate deputy attorney general, Brian Nieves. 

Judge Margaret M. Garnett said last month that the social media posts likely violated the court’s order and asked the department to explain how the violation occurred.

In a Wednesday legal filing, federal prosecutors argued that the incident did not jeopardize Mr. Magione’s right to a fair trial because the two staffers “operate entirely outside the scope of the prosecution team, possess no operational role in the investigative or prosecutorial functions of the Mangione matter, and are not ‘associated’ with this litigation.” 

Prosecutors also noted that once they became aware of the posts, they “promptly directed” the staffers to take them down. They further argued that the significant time remaining before a trial date makes it unlikely the posts would affect potential jurors.

The incident represents just the latest challenge to the government’s prosecution strategy.

In April, Judge Garnett imposed a gag order barring public comments about the case after the attorney general, Pam Bondi, made a series of statements announcing her decision to pursue capital punishment. Ms. Bondi characterized the killing as “a premeditated, cold-blooded assassination that shocked America” and explicitly tied the decision to “President Trump’s agenda to stop violent crime and Make America Safe Again.”

Those comments prompted Mr. Mangione’s defense team to seek the dismissal of federal charges and removal of the death penalty. Now, with additional alleged violations, they’re renewing that argument with more ammunition.

The defense has also flagged statements by Mr. Trump himself and other administration figures, including the White House press secretary, Karoline Leavitt, arguing these comments have irreparably prejudiced the jury pool. 

Mr. Mangione faces federal murder and stalking charges in connection with the December shooting death of the UnitedHealthcare CEO, Brian Thompson, outside a Manhattan hotel. The 27-year-old accused killer has pleaded not guilty to all charges. In September, the court dismissed terrorism charges against him.