The murder case, which starts with opening statements in Suffolk Superior Court today, has drawn significant public attention.

Mangione's lawyers have argued that items recovered from his backpack, including a 3D-printed handgun and notebook, should not be admissible because police searched the bag without a warrant.

Luigi Mangione is due back in court on Tuesday for the second day of a hearing in his bid to bar New York prosecutors from using some key evidence they say links him to last year’s killing of UnitedHealthcare CEO Brian Thompson.

Lawyers for former downstate sheriff's Deputy Sean Grayson allege the judge in the case erred multiple times ahead of the jury's second-degree murder verdict. Prosecutors say the claim lacks merit.

Another delay has been set in Nicholas Wayne Moore’s long-pending sexual conduct case, which will move forward only after his ongoing murder trial concludes before a different judge.

Security around the high-profile trial has been tightened, with officers moved in to neutralise the threat and protect those at risk.

Body camera video shown in court Tuesday documented how police approached, arrested and searched Luigi Mangione at a Pennsylvania McDonald's — moments that underlie key questions about what evidence will and won't be allowed at his eventual state murder trial in the killing of UnitedHealthcare CEO Brian Thompson.