Luigi Mangione’s defense attorney in Pennsylvania continues to argue that Altoona police unlawfully detained the murder suspect and searched his belongings when they identified him at a McDonald’s following a tip.

Mangione, 26, is charged with first-degree murder in furtherance of an act of terrorism, stalking and a slew of other state and federal charges in both New York and Pennsylvania, for allegedly gunning down UnitedHealthcare CEO Brian Thompson, a married father of two, on a sidewalk in Manhattan in December 2024.

Now his attorney says authorities’ use of the word “manifesto” to describe Mangione’s writings allegedly found in his backpack during his arrest on Dec. 9 is “incorrect.”

“The use of this characterization of the defendant’s alleged personal experiences and writings is incorrect, improper and without justification and has no probative value,” Altoona-based defense attorney Thomas Dickey said in a Tuesday court filing. “Defendant believes that this characterization was done so solely for the purpose to prejudice the defendant and put him in a negative light before the public, all in an effort to prejudice any potential jury pool.”

The suspected gunman in UnitedHealthcare CEO Brian Thompson’s murder, believed to be Luigi Mangione, is seen flirting with a hostel employee on surveillance footage before the Dec. 4 shooting. (NYPD)

The suspect allegedly fled the scene of Thompson’s murder, rode a bike to a bus station and took a bus to Altoona, where he was ultimately identified and arrested.

Mangione is originally from Maryland and recently lived in California and Hawaii. He graduated as valedictorian from the Gilman School, a private, all-boys high school in Baltimore, in 2016.

Mangione went on to receive his bachelor’s and master’s degrees in computer science from the University of Pennsylvania in 2020.

Fox News Digital’s Michael Ruiz contributed to this report.