The United States of Leland (2003)

What it's about

A withdrawn young man, Leland Fitzgerald is imprisoned for the murder of a mentally disabled boy, who also happened to be the brother of his girlfriend, Becky. As the community struggles to deal with the killing, Pearl Madison, a teacher at the prison, decides to write about Leland's case. Meanwhile, others affected by the murder, including Becky and her sister, Julie, must contend with their own problems.