What techniques does Harper Lee use to show racism and loss of innocence in To Kill a Mockingbird?

Racism and racial prejudice are among the most significant themes in To Kill a Mockingbird, but they aren't always obvious. As such, it can be considered a motif, which is its own literary technique. Some characters like the Ewells are overtly racist, but the racism harbored by other characters is much more subtle and Lee uses a variety of techniques to convey their feelings. Aunt Alexandra, for example, uses terms like "those people" or other coded language to convey her feelings about those she feels are inferior. For instance, when discussing the family lineage with the children, she uses the term "gentle breeding" to imply that their family is superior to other types of people. Moreover, Aunt Alexandra asks a lot of rhetorical questions, particular when speaking with Atticus about Jem and Scout. These help the reader to better-understand her feelings about race and class without her ever having to use racist language.

Regarding Lee's emphasis on innocence, that is often described in metaphor. The title of the book, for example, is a reference to a statement made by Atticus about how it's a sin to kill a mockingbird. The metaphor implies that it is sinful to take away the innocence and purity of something that only wanted to do something kind. This metaphor frequently applies to Scout, who begins the book as the picture of innocence but comes away at the end with a better understand of how people she thought were good could behave so cruelly.

Tom is another character that reflects the metaphoric title of the book. If he hadn't stopped to help Mayella, he wouldn't be on trial. In that way, Tom's desire to do something nice for someone else has ultimately led to his literal and figurative loss of innocence.