One year to the day after UnitedHealthcare CEO Brian Thompson was fatally shot on a Manhattan sidewalk, the man accused in the killing — 27-year-old Luigi Mangione — returned to court Thursday as a pivotal evidentiary hearing in his state murder case entered its third day.

Mangione’s attorneys are urging the judge to bar prosecutors from using key evidence, including the alleged murder weapon and the defendant’s personal journal. They argue that the items were taken unlawfully from Mangione’s backpack during his arrest because officers did not have a warrant.

The outcome of the hearing could significantly weaken the prosecution’s case, as the disputed evidence is among what they describe as the strongest proof of Mangione’s guilt. The proceedings have also provided the most detailed look yet at how prosecutors intend to present their case at trial.

Mangione watched alongside his defense team as video footage of the shooting — appearing to show him firing into Thompson’s back — was played in court. Jurors also heard testimony from the officer who arrested him at a McDonald’s in Altoona, Pennsylvania.

“It’s him. I have been seeing all the pictures. He is nervous as hell,” Altoona police officer Joseph Detwiler testified Tuesday. “I ask him, ‘Have you been in New York?’ He’s all quiet.”

So far, prosecutors have called six witnesses, aiming to show that Mangione’s arrest five days after the killing was lawful. They presented security footage from inside the McDonald’s showing Mangione entering around 9 a.m., a recording of the manager’s 911 call, and body-camera video of officers approaching Mangione before placing him into custody.

Defense lawyers are focusing heavily on the roughly 20-minute gap between the officers’ initial interaction with Mangione and his formal arrest. They argue his constitutional rights were violated because police questioned him and obtained statements before reading his Miranda rights.

During his full-day testimony, Detwiler recounted the dramatic arrest, saying he initially doubted the legitimacy of the tip that led police to the fast-food restaurant — so much so that he didn’t activate his sirens while responding. But once he asked Mangione to lower his face mask, Detwiler said, “I knew it was him immediately.”