In New York, as the somber one-year mark of UnitedHealthcare CEO Brian Thompson’s murder approaches, a critical courtroom battle is set to unfold. The focus is on Luigi Mangione, who stands accused of the crime, as he seeks to prevent key evidence from being presented in his upcoming trial. This week, Mangione will face hearings beginning Monday, where he aims to convince the court to exclude certain items that prosecutors argue tie him to the fatal incident.

The prosecution’s evidence includes a 9 mm handgun, purportedly the weapon used in Thompson’s killing on December 4, 2024, and a notebook allegedly containing Mangione’s ominous plan to target a health insurance executive. These items were seized during Mangione’s arrest, but his legal team is challenging their admissibility in a yet-to-be-scheduled state murder trial.

Recently, Mangione achieved a legal victory by having state terrorism charges dismissed in September. Now, his defense is focusing on what they claim were violations of his constitutional rights during his arrest, arguing that these issues could compromise his right to a fair trial.

Central to their argument is the assertion that the evidence, including the gun found in a backpack, was obtained without a warrant, which they believe renders it inadmissible. Additionally, they are seeking to exclude certain statements Mangione allegedly made to police, such as providing a false identity, on the grounds that he was questioned before being informed of his Miranda rights.

They contend that the gun and other items should be excluded because police lacked a warrant to search the backpack in which they were found. They also want to suppress some of his statements to police, such as allegedly giving a false name, because officers started asking questions before telling him he had a right to remain silent.

Eliminating the gun and notebook would be critical wins for Mangione’s defense and a major setback for prosecutors, depriving them a possible murder weapon and evidence they say points to motive.

The Manhattan District Attorney’s Office has quoted extensively from Mangione’s handwritten diary in court filings including his praise for Unabomber Ted Kaczynski.

In it, prosecutors say, Mangione mused about rebelling against “the deadly, greed fueled health insurance cartel” and said killing an industry executive “conveys a greedy bastard that had it coming.”

Mangione has pleaded not guilty to state and federal murder charges. The state charges carry the possibility of life in prison, while federal prosecutors are seeking the death penalty.

Mangione’s lawyers want to bar evidence from both cases, but this week’s hearings pertain only to the state case. The next hearing in the federal case is scheduled for Jan. 9.

Court officials say the hearings beginning Monday could take more than a week. If that holds, Mangione is almost certain to be in court on the anniversary of Thompson’s death on Thursday.

Defense lawyer Marc Agnifilo told a judge in an unrelated matter last week that Manhattan prosecutors could call more than two dozen witnesses.

Thompson was killed as he walked to a Manhattan hotel for his company’s annual investor conference. Surveillance video showed a masked gunman shooting him from behind. Police say “delay,” “deny” and “depose” were written on the ammunition, mimicking a phrase used to describe how insurers avoid paying claims.

Mangione, the Ivy League-educated scion of a wealthy Maryland family, was arrested five days later at a McDonald’s in Altoona, Pennsylvania, about 230 miles (about 370 kilometers) west of Manhattan.

Prosecutors in the state case have not responded to the defense’s written arguments.

An officer searching a backpack found with Mangione was heard on a body camera recording saying she was checking to make sure there “wasn’t a bomb” in the bag. His lawyers argue that was an excuse “designed to cover up an illegal warrantless search of the backpack.”

Federal prosecutors, fighting similar claims in their case, have said in court filings that police were justified in searching the backpack to make sure there were no dangerous items. His statements to officers, federal prosecutors said, were made voluntarily and before he was taken into police custody.