There are two additional references to previous roles Robert Duvall has played: 1) The bailiff's name is Augustus or Gus....Duvall has often said that the role of Augustus McCrae was one of his favorites. There's a bit of a gleam and a subtle smile when Duvall's character says "Gus". 2) When Sam and Hank are discussing their past at the lake, Sam uses the phrase "A more superior prick never shit between two shoes". Duvall's character in "The Great Santini" is described as "The greatest marine fighter pilot that ever crapped between two shoes!"
WARNING this is a spoiler for Twin Peaks Grace Zabriskie, who plays Mrs. Blackwell, was Laura Palmer's mom in Twin Peaks the TV series where Laura was killed by her father Mr Palmer. In "The Judge" her son is also killed by Mr Palmer.
As filmed from an interior viewpoint, Mark Blackwell's mother spits on the car door window. In the following external shot of the car driving off, the same window is clean of any spit. The spit is again visible on the window in the next shot back in the car.
The sheriff's patrol cars in this movie have all-blue lightbars. In the State of Indiana, where the film is set, all police vehicles must have red flashing lights (even if used in combination with other colors).