Answer:
To Kill a Mockingbird by Harper Lee is full of instances of both justice and injustice, and most of them happen outside of the courtroom. In fact, the most obvious miscarriage of justice happens in a courtroom but is redressed outside of it. Both Cecil Jacobs and the Finches' cousin Francis are served a little justice by Scout in the form of a physical blow. Both boys accuse Atticus of being a bad lover who defends guilty black men, and both of them get punched for saying it. This is a form of "fair treatment and due reward" for their insults. Neither boy is punished (in fact, Scout is the one who gets punished), but Scout upholds what she sees as justice ("fair treatment") in the most obvious (and admittedly reactionary) way she knows how.
Hope this helps) Sky