NEW YORK — As the one-year mark of UnitedHealthcare CEO Brian Thompson’s tragic death approaches, the man accused of his murder is set to appear in court this week. The proceedings will focus on whether certain evidence, which prosecutors claim ties him to the crime, can be used in the trial.

Luigi Mangione, 27, faces hearings beginning Monday as he attempts to prevent the Manhattan District Attorney’s Office from presenting items obtained during his arrest at a still-to-be-scheduled state murder trial.

Among the contested evidence is a 9 mm handgun, which prosecutors allege is the weapon used in the December 4, 2024, murder. Additionally, a notebook purportedly containing Mangione’s written intent to harm a health insurance executive is under scrutiny.

With state terrorism charges against Mangione previously dismissed in September, his legal team is now challenging what they describe as unconstitutional police actions that compromised his arrest and could jeopardize his right to a fair trial.

Mangione’s attorneys argue that the gun and other items should be excluded from evidence because the police did not have a warrant to search the backpack where they were found. They are also working to suppress some of his statements to law enforcement, claiming officers questioned him before reading his Miranda rights, leading to him allegedly providing a false name.

If successful in excluding the gun and notebook, Mangione’s defense would achieve significant victories, while prosecutors would face a considerable setback, losing potentially crucial evidence of both a murder weapon and the defendant’s alleged 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.

The Associated Press contributed to this report.