NEW YORK (AP) — In a dramatic courtroom scene, Luigi Mangione is contesting the legitimacy of critical evidence linked to the murder of UnitedHealthcare CEO Brian Thompson, as police testimonies detailed the circumstances surrounding his arrest.

Moments after being handcuffed at a Pennsylvania McDonald’s, police discovered a loaded gun magazine wrapped in underwear tucked within Mangione's backpack. This finding bolstered the belief among officers that he was the suspect in Thompson's murder, which occurred just days earlier in Manhattan.

An officer's reaction, captured on bodycam footage, confidently declared, “It’s him, dude. It’s him, 100%,” as they sifted through Mangione’s belongings. The evidence, including a handgun and a handwritten notebook, is currently at the center of a pretrial hearing where Mangione is seeking to exclude it from being used against him.

At 27 years old, Mangione has pleaded not guilty to both state and federal murder charges. During the hearing, he appeared attentive, often taking notes while watching video evidence presented in court.

Prosecutors claim that the handgun linked to the case matches the weapon used in Thompson's assassination, while writings in the notebook outlined Mangione's disdain for health insurers and explicit thoughts about targeting a CEO at an investor conference.

Mangione's legal team argues that the police lacked a search warrant when they examined his backpack. Prosecutors counter that the search was justified under police protocols requiring swift searches for potentially dangerous items at the time of arrest. They also mentioned that a warrant was later obtained for a follow-up search.

Police Officer Christy Wasser, who has served on the Altoona police force for nearly twenty years, stated that she had seen related news coverage of Thompson’s murder before responding to the McDonald’s, where Mangione's resemblance to the suspect had drawn a 911 call.

Upon arrest, Mangione had invoked his right to remain silent but was still subjected to a search, leading to the initial discovery of innocuous items such as food and a cellphone before the firearm-related evidence was revealed. The items found sparked concerns of potential threats, prompting further searches at the police station where even more evidence followed.

As the legal battle intensifies, Mangione's defense is pushing back against what they term prejudicial language from prosecutors describing Thompson's death as an execution—language they argue could bias jurors.

The case continues to unfold as the courtroom deliberates the admissibility of this poignant evidence, with serious implications for both the prosecution and defense in the high-profile murder trial.