New York, New York - Luigi Mangione, accused of gunning down a health insurance executive in New York, will use a psychiatric defense at his highly anticipated state murder trial, media reported Wednesday.

Mangione's lawyers will argue that he was suffering from an "extreme emotional disturbance" – a partial defense that can reduce a sentence, unlike an insanity plea, which seeks to avoid criminal responsibility altogether.

The December 2024 murder of UnitedHealthcare CEO Brian Thompson, captured on surveillance video, shocked the US and highlighted public anger with the country's private health system.

Five days after the killing, Mangione was arrested at a McDonald's in Altoona, Pennsylvania, 230 miles from the crime scene, following a tip from a staff member.

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Mangione is charged in state court with murder and faces possible life imprisonment without parole. The trial is set to begin on September 8.

In May, the judge decided to exclude certain items of evidence, including a handgun magazine, a phone, and a wallet, after Mangione's lawyers argued an initial police search breached procedure.

However, other key items recovered can be used: a 9mm pistol, a silencer, and a notebook containing criticism of the US health insurance system.

Mangione is also charged in federal court with two counts of interstate stalking and risks the same punishment.

Two other federal charges that carried the death penalty were thrown out by a judge earlier this year.

Defendants in the US can be tried at both the state and federal level for the same crime, although the charges tend to differ.