The former tight end is already serving a life sentence in the 2013 killing of semi-pro football player Odin Lloyd.
Hernandez is accused of gunning down Daniel de Abreu and Safiro Furtado after one of the men accidentally spilled a drink on him. He has pleaded not guilty.
Florida attorney Jose Baez — who successfully defended Casey Anthony in her 2011 trial in the death of her daughter — and Harvard Law School professor Ronald Sullivan are now representing Hernandez.
Hernandez was indicted in Suffolk County, but the hearing is being held in Plymouth County, where Judge Jeffrey Locke is currently assigned.