Green’s Dictionary of Slang

(US prison) a particularly unappealing item of food served to prisoners in solitary confinement; the meal consists of a ground patty, approx. 10 × 10 × 8cm (4 × 4 × 3in), which is composed of the entire meal’s ingredients put together through a blender; it is trad. burned on the outside and raw within.

1931		San Quentin Bulletin Jan. 11: Hamburger balls are entitled jute-balls.
1992		Bentley & Corbett Prison Sl. 11: Judy also Jupe Balls The name for the meals that are served in the hole or lockdown areas. This meal is part of an offender’s punishment. Judy is a ground patty 4" x 4"x 3" that is made up of the entire meal’s ingredients and is run through a grinder. They are traditionally served burned on the outside and raw on the inside.