Luigi Mangione, accused of shooting UnitedHealthcare CEO Brian Thompson outside a Manhattan hotel last December, is entering a crucial week-long pretrial hearing in New York state court.

The hearing will focus on whether the evidence collected against him was obtained legally and if his statements to police violated his constitutional rights.

Mangione’s defense is pushing hard to have key evidence, including a red notebook described by authorities as a "manifesto," tossed out, arguing the items were seized after an illegal search and that he was interrogated without Miranda warnings.

“The hearing could last at least a week. Marc Agnifilo, one of Mangione’s attorneys, said he expects prosecutors to call as many as 28 witnesses — including some from Altoona, Pennsylvania, where Mangione was apprehended last December at a McDonald’s restaurant days after the shooting,” reports NBC News.

“The proceedings are set to be divided into two sections. Both will focus on whether any evidence or statements were obtained illegally and should be excluded from trial.”

Judge Gregory Carro is overseeing the two-stage pretrial process: 

• In the first part, known as a Mapp hearing, Carro will hear testimony and arguments before deciding whether the police had a legal right to obtain physical evidence.

• In the second, known as a Huntley hearing, Carro will review evidence before ruling whether statements Mangione made to law enforcement were coerced or obtained in violation of his rights.

Carro’s rulings will determine the extent of evidence the prosecution can present at trial, and could potentially make or break the case against Mangione.

Karen Agnifilo, another Mangione attorney, said the defense is not expecting a third section known as a Mosley hearing, which focuses on whether a non-eyewitness can testify about whether a person in a video or photo is Mangione.

Mangione has pleaded not guilty to nine state charges and four separate federal counts, the latter carrying the possibility of the death penalty.

The defense claims police conducted a warrantless search of Mangione's backpack at a McDonald's in Altoona, Pennsylvania, where he was arrested days after the shooting. 

They argue this search violated the Fourth Amendment, making any evidence recovered—including a 3D-printed ghost gun, fake IDs, ammunition, and his writings—inadmissible.

They also contend that officers failed to promptly read Mangione his Miranda rights, questioned him without informing him of his right to remain silent, and thereby violated his Fifth Amendment protections. The defense attorney Karen Agnifolo stressed the prejudice caused by the "manifesto" label and improper police procedures in detaining and interrogating Mangione.

“Law enforcement has methodically and purposefully trampled his constitutional rights by interrogating him without Miranda warnings in violation of the Fifth Amendment and illegally searching his property without a warrant in violation of the Fourth Amendment,” Agnifilo claimed in a statement.

Prosecutors claim Mangione planned the attack by traveling to New York, stalking Thompson, and killing him. Ammunition at the scene was engraved with words like “delay,” “deny,” and “depose,” reflecting grievances against the healthcare industry found in Mangione’s writings. Surveillance footage, including a viral shooting video, captured Mangione’s movements before and after the assassination. The prosecution intends to use this evidence to secure a conviction in what is expected to be a high-profile trial.

Mangione became something of a celebrity on the political left after his capture. Saturday Night Live’s audience even applauded at the mere mention of him. Back in February, CNN’s Kaitlan Collins casually shared Mangione’s legal defense site on social media. In June, a musical about Mangione opened in San Francisco.

The coming days will reveal whether prosecutors can keep their case intact or whether the defense’s sweeping claims of constitutional abuse gain traction, but the stakes stretch far beyond the courtroom.

The hearings will show if a man embraced by the left will be held accountable for the execution-style killing that stunned the country last year.