It is perceived that a court should be an un-bias means of determining the guilt or innocence of the accused. This is not always the case with racial, social and personal prejudices influencing decisions.
It is clear in 'To Kill a Mockingbird' that there is racial prejudices in the town, when Atticus is assigned the job of defending a 'nigga' in a rape case he knows that there is no hope for Tom Robertson he still defends him and tries to fight a fair case, but unfortunately the townspeople's racial prejudices influence the decision.
"The one place where a man ought to get a square deal is in a courtroom, be he any colour of the rainbow, but people have a way of carrying their resentments right into a jury box. As you grow older, you'll see white men cheat black men every day of your life, but let me tell you something and don't you forget it - whenever a white man does that to a black man, no matter who he is, how rich he is, or how fine a family he comes from, that white man is trash."
~Atticus, page 243
Atticus is one of the few people in Maycomb that actually fights for justice even though he knows it is a losing battle, but he truly respects people for what they are, not the colour of their skin.
Not all people feel that people can be decent if they are black, most people in the town would not give a black person a chance at all to prove themselves, or help them even if they knew they could do a good job.
"... you've got to do something about her," - Aunt Alexandra
This is said by the aunt when she and Atticus are...