In documents submitted to the Manhattan federal court, the defense argued that prosecutors should be barred from presenting Mangione’s statements to law enforcement and evidence from his backpack, which contained a gun and ammunition, during the trial.

The lawyers contended that Mangione was not informed of his rights prior to being interrogated by officers, following his arrest after Brian Thompson’s fatal shooting while arriving at a Manhattan hotel for an investor event.

Last month, Mangione’s attorneys sought dismissal of his federal charges and the exclusion of the death penalty due to public remarks by US Attorney General Pam Bondi.

In April, Bondi instructed New York prosecutors to pursue the death penalty, describing Thompson’s murder as a “premeditated, cold-blooded assassination that alarmed the nation.”

While murder cases are typically handled in state courts, Mangione faces additional charges under a federal statute concerning firearm-related murders in conjunction with other “violent crimes.”

It’s the only charge for which Mangione could face the death penalty, since it’s not used in New York state.

The papers filed early on Saturday morning (New York time) argued that this charge should be dismissed because prosecutors have failed to identify the other offences that would be required to convict him, saying that the alleged other crime — stalking — is not a crime of violence.

The assassination and its aftermath have captured the American imagination, setting off a cascade of resentment and online vitriol toward US health insurers while rattling corporate executives concerned about security.

After the killing, investigators found the words “delay,” “deny” and “depose,” written in permanent marker on ammunition at the scene.

The words mimic a phrase used by insurance industry critics.