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In Harper Lee's To Kill a Mockingbird, I believe that Heck Tate is symbolic in several ways.
Heck Tate is symbolic of society's laws. It is no coincidence that Heck is the sheriff. He is the man the town looks to in order to uphold the law. Heck Tate is also a take-charge kind of person. He goes to Atticus when Tim Johnson shows up, knowing that Atticus can handle the problem with an expertise no one else has. Heck sees the world in shades of black and white: right and wrong. But he is also able to see the shades of grey as well.
Ironically, at the end of the story, Heck Tate becomes the voice of reason that protects the story's hero. In doing so, Heck is also protecting an innocent member of Maycomb, who has been abused by his family and would be further tormented by the attentions (though well-meant) of society should it discover the hand Boo Radley had in saving the Finch children from Bob Ewell's attempts of murder.
Heck Tate is symbolic of justice. He sees justice in Ewell's death, but he also sees—just as clearly—a need for justice for Boo Radley, a mockingbird that does nothing to harm anyone else. It is here that Heck Tate can see the shades of grey, and the need to protect an innocent man.