There are several ways in which the movie A Time to Kill and To Kill a Mockingbird are similar.
First, both stories deal with black men who have been accused of a crime, tried in a court of white males in the South. (In both movies, a rape has taken place or has been alleged to have taken place.)
Second, in both movies, the lawyers are committed to doing what they are able to give each black man a fair trial.
Third, racism plays an enormous role in what the verdict of the trial will be.
A Time to Kill is based on a John Grisham novel written in the 1980s. In the film adaptation, the author addresses the rape of a young black girl by two white men, irrefutable evidence of the guilt of those men, the sense that the rapists will go free, and the father's decision to take the law into his own hands, believing a trail in the South will never convict white men for the rape of a black child.
Set in Canton, Mississippi, the film revolves around the rape of a young girl and the arrest of the rapists and their subsequent murder by the girl's father, Carl Lee Hailey.
In To Kill a Mockingbird, based on Harper Lee's novel, racial inequality also plays a large part. In addition, there is also irrefutable evidence to exonerate Tom Robinson of his guilt in Mayella Ewell's "rape," but it is disregarded—because the word of a white woman would never be doubted in the Depression South because of the words of a black man.
...the primary themes of To Kill a Mockingbird involve racial injustice and the destruction of innocence.
The theme of "loss of innocence" is also present in both movies: in A Time to Kill, Carl's daughter's rape robs her of her innocence (among other things); in the movie To Kill a Mockingbird, it is primarily Scout (and to an extent, Jem) who loses her innocence in learning of the evil that resides in some men (and the goodness in others), even as Bob Ewell tries to murder Scout and Jem one dark night.
There are several strong similarities between the two movies.