In terms of prejudice and lack of justice in Harper Lee's To Kill a Mockingbird, there is a great deal found in the court case trying Tom Robinson for allegedly raping Mayella Ewell. In fact, this portion of the novel overflows with prejudice, and the lack of justice is seen specifically with the outcome of the trial.
With regard to prejudice, this can be seen as children in the school yard (Cecil Jacobs) give Scout a hard time because her father is defending a black man, or in the way Mrs. Dubose insults Atticus in front of Jem and Scout:
"And you"—she pointed an arthritic finger at me—"what are you doing in those overalls? You should be in a dress and a camisole, young lady! You'll grow up waiting tables if somebody doesn't change your ways—a Finch waiting on tables at the O.K. Cafe—hah!"
I was terrified...I grabbed Jem's hand but he shook me loose.
"Come on, Scout," he whispered. "Don't pay any attention to her, just hold your head high and be a gentleman."
But Mrs. Dubose held us: "Not only a Finch waiting on tables but one in the courthouse lawing for n***ers!"
The same prejudice is seen when Scout's cousin Francis says something similar and she punches him in the mouth. It is apparent again when Bob Ewell spits in Atticus' face when they meet on the street. Prejudice drives Ewell also to follow Helen Robinson to work, whispering vulgarities at her back. The mob that shows up at the jail to lynch Tom Robinson demonstrates its prejudice.
At the same time, there is also prejudice shown against Boo Radley. The community makes up terrible stories about this unfortunate man who was abused by his family and now is little more than a ghost. As far as anyone knows, none of what they say is true. Boo is not a frightening, dangerous creature, which is proven by the story's end.
A lack of justice is witnessed at the end of Tom Robinson's trial. Obviously Tom could never have raped Mayella Ewell; his crushed and useless arm proves that it was impossible for him to attack her. Mayella was beat up by someone who was left-handed; Tom couldn't use his left hand. This fact clearly demonstrates Tom's innocence. However, most of the jury is prejudice, as is the community of Maycomb, and Tom is found guilty. This travesty of justice devastates Jem. Scout recalls:
I shut my eyes. Judge Taylor was polling the jury: "Guilty...guilty...guilty...guilty..." I peeked at Jem: his hands were white from gripping the balcony rail, and his shoulders jerked as if each "guilty" was a separate stab between them.
After the courtroom has cleared, Scout continues:
It was Jem's turn to cry. His face was streaked with angry tears as we made our way through the cheerful crowd. "It ain't right," he muttered, all the way to the corner of the square where we found Atticus waiting...
"It ain't right, Atticus," said Jem.
"No son, it's not right."
Besides the wonderful story and memorable characters, another reason this novel has such an impact is because it draws attention to "race relations" in the South during the Great Depression. Whereas it hit the entire country hard, it was tougher in the South, which was still recovering from the Civil War. Many people in that region saw the emancipation of slaves as the direct cause for the fall of the South.
The novel was published in 1960 as the Civil Rights Movement was just starting to gain momentum. It struck a nerve most especially because of the prejudice conveyed and the lack of justice for black Americans.