Matthew McConaughey was originally cast as Freddie Lee Cobb. After reading the script, he preferred the role of Jake Brigance. He went to director Joel Schumacher, who granted him a private screen test.
Soon after the murders, Jake is tormented by guilt. He admits to Carla that he didn't tell anyone about Carl Lee's plans, because he didn't believe Carl Lee would go through with them. In the book, he does tell the Sheriff, but the Sheriff is the one who downplays the potential danger.