Mangione, 27, is accused of fatally shooting Brian Thompson, who was CEO of UnitedHealth Group's health insurance unit, on a sidewalk in Midtown Manhattan in December 2024.
Public officials condemned the assassination but Mangione became something of a folk hero to some critics of steep US healthcare costs and insurer practices.
Mangione, dressed in prison garb for Friday's hearing, was escorted by law enforcement into a courtroom packed with observers.
He previously pleaded not guilty to federal murder, stalking and weapons charges and has been behind bars while awaiting trial.
At the hearing before US District Judge Margaret Garnett in Manhattan, Mangione's lawyers will argue that a charge of murder with a firearm - the only one that carries the possibility of the death penalty - should be dismissed because prosecutors did not meet the legal requirements for such a charge.
Garnett is separately weighing Mangione's bid to throw out the indictment altogether and bar prosecutors from seeking the death penalty because they allegedly violated his constitutional rights.
New York's death penalty was declared unconstitutional in 2004 but the ban applies in state, not federal cases.
Mangione also faces state-level criminal charges, including murder, and could be sentenced to life in prison if convicted.
No trial date has been set in either case.
