Despite losing a similar argument in federal court at the end of January, accused CEO assassin Luigi Mangione's defense team is again vying to have damning evidence from his backpack suppressed in a New York state court.

Prosecutors have said police recovered the suspected murder weapon and a manifesto railing against the health insurance industry in the bag, and they've defended the search as proper.

Mangione, 27, is accused of assassinating UnitedHealthcare CEO Brian Thompson, 50, on Dec. 4, 2024 — allegedly shooting him in the back outside a Manhattan hotel slated to host a shareholder conference later that morning.

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According to prosecutors, he skipped town and went to Altoona, Pennsylvania, before people in a McDonald's restaurant recognized him from a wanted poster and called 911.

It's the search of his bag that happened there after his arrest that the defense is calling into question, writing in court documents that New York search and seizure rules apply since that's where the case is headed to trial.

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Read the filing:

Authorities searched the bag multiple times after Mangione's arrest in the eight hours before obtaining a search warrant, defense lawyers wrote in a letter to Manhattan Judge Gregory Carro.

They have claimed that the bag search was inappropriate because it was no longer in Mangione's "possession" once he was arrested and that the claim that they were looking for potentially dangerous material, like a bomb, was a false pretext.

"The totality of the circumstances demonstrates that the officers' claim about a bomb was a blatantly false and pretextual justification for conducting an evidentiary search," wrote defense lawyer Karen Friedman Agnifilo.

And they argued that police did not write down non-evidentiary items in the bag when filling out an inventory and alleged that police improperly read Mangione's journals before they obtained a search warrant.

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"[Altoona Police] Sergeant Heuston did not happen to 'notice' Mr. Mangione's writings; he purposefully read through the journal looking for incriminating writings, photographed what he deemed to be incriminating writings and forwarded them to the NYPD," the filing reads.

Since the first responding officer testified that he recognized Mangione from the NYPD's highly publicized wanted poster and Altoona police soon were in contact with their NYPD counterparts, Mangione's defense argued that police should have known their handling of the case would be subject to New York law.

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They have also argued that additional searches at the police precinct building were also improper.

The defense alleges that one officer was motivated "to get credit for finding the alleged murder weapon in a case that had captivated the country for nearly five days" and made sure her body camera audio was working before opening the compartment where she found a gun.

Although Mangione faces serious charges in the alleged assassination, his legal team has won a string of victories in both state and federal courts — having the top charges in each case thrown out. As a result, if convicted of the top remaining charges, he would not face the potential death penalty federally or life in prison without the possibility of parole in New York.

In Mangione's federal case, which is a separate legal proceeding, U.S. District Judge Margaret Garnett ruled that the backpack evidence could stand in his federal trial in a Jan. 30 order, while also dealing a blow to the prosecution and taking the death penalty off the table.

He may lose one of his high-powered lawyers in that case after the victory. Garnett has asked whether taxpayer funding for attorney Avi Moskowitz, an expert death penalty defense lawyer, is still necessary. Federal prosecutors declined to take a position on the issue, and the defense filed an ex parte letter under seal.

Both trials are slated to begin later this year, but it's not clear whether the scheduling is realistic.

Thompson, a father of two from Minnesota, had come to New York City to meet with Wall Street investors. Surveillance video shows the last moments of his life — when a gunman approached him from behind on the sidewalk and opened fire.

Carro is expected to announce his ruling on the motion to suppress on May 18, which is also the date of Mangione's next scheduled hearing at the state level.