Luigi Mangione, the man accused of fatally shooting United Healthcare CEO Brian Thompson in Manhattan a year ago this week, appeared in court on Monday as his lawyers challenge the admissibility of key evidence in his case.
Mr Mangione, 27, has pleaded not guilty to both state and federal murder charges, which carry the possibility of the death penalty.
The pre-trial hearing could last several days, as defense attorneys are expected to call a host of witnesses, including from Pennsylvania, where he was arrested at a McDonald's.
In September, a judge threw out state terrorism-related murder charges against Mr Mangione, arguing prosecutors had failed to establish evidence to justify them.
Mr Mangione's legal team is now hoping to convince a judge to exclude evidence including a gun and a notebook in which prosecutors say he set out a motive.
The defendant was arrested days after he allegedly shot Mr Thompson, a father of two, as he was walking into an investors' conference on a busy Manhattan street on December 4, 2024.
A date for either of his trials has not yet been set.
Walking into court on Monday, Mr Mangione wore a grey suit and shirt, and court employees removed his hand restraints before he sat, as his lawyers requested.
This week's hearing focuses on whether prosecutors illegally obtained evidence from Mr Mangione when they arrested him in Altoona, Pennsylvania, and whether it should be excluded as a result.
Defense attorneys are seeking to suppress some of Mr Mangione's statements he made to police after being arrested - including allegedly giving them a false name.
They argue he did so before police read him his rights, including the right to remain silent.
His attorneys are also hoping to exclude from the trial a 9mm handgun that prosecutors say matches the one used in the killing, as well as writings found in Mr Mangione's backpack.
Prosecutors have alleged that Mr Mangione - the scion of a prominent Maryland family who graduated from an Ivy League university - had written in his notebook about the deadly, greed fueled health insurance cartel.
But defense lawyers are arguing his backpack was searched without a warrant, and the items found in it should be excluded for that reason.
Eliminating those two critical pieces of evidence would be a big win for Mr Mangione's legal team.
However, the chances of that happening are virtually non-existent, said Dmitriy Shakhnevich, a criminal defense attorney in New York.
He explained that there are a number of exceptions to constitutional rules that law enforcement must obtain a warrant for personal searches, including those covering this case.
As the hearing continues, prosecutors assert they have other critical evidence, including DNA or fingerprints on items discarded near the crime scene. Analysts have also reviewed CCTV footage showing the incident and testimonies from individuals present during and after the shooting.
The implications of this case extend beyond Mr Mangione himself, involving broader discussions over justice, law enforcement practices, and the rights of defendants in serious criminal cases.
