Luigi Mangione is due to appear in a New York courtroom on Tuesday for what could be the final hearing before his state murder trial begins next month.

In a surprise turn of events, Luigi Mangione pleaded guilty to federal stalking charges in the killing of United Healthcare CEO Brian Thompson.

A guilty plea would avert a federal trial in the closely watched case over the killing of UnitedHealthcare CEO Brian Thompson, a brazen crime that was condemned by public officials but became emblemat...