How does Harper Lee capture Dill's lost childhood innocence in To Kill a Mockingbird?

In To Kill a Mockingbird, author Harper Lee depicts Dill as an innocent child who loses his innocence in Maycomb.

Dill's childishness is especially characterized in the whopping tales he tells. For example, when he has trouble explaining to Scout that he ran away from his home in Meridian because he felt neglected by his mother and new stepfather, he concocts a story that you can row a boat "across to a foggy island where all these babies were; you could order one--" (Ch. 14). He continues in his story to describe the magical island where "babies slept, waiting to be gathered like morning lilies" (Ch. 14).

Dill's innocence is especially captured when Dill begins uncontrollably crying during Mr. Gilmer's cross-examination of Tom Robinson during the trial. As Mr. Dolphus Raymond points out, Dill is not crying because he's overly sensitive; he's crying because he still has the ability to be sickened by evils that go on around him. The older we get, sadly, the more desensitized we become to the evils around us. Mr. Raymond points out the fact that we become desensitized when he further makes the following speech:

Let [Dill] get a little older and he won't get sick and cry. Maybe things'll strike him as being--not quite right, say, but he won't cry. (Ch. 20)

In other words, Dill will no longer cry because, though he will still be able to recognize evil as evil, he'll be so accustomed to witnessing it that he will have been hardened and no longer cry.

The more time Dill spends in Maycomb, the more the reader observes Dill growing up and losing his childhood innocence. One example of his loss of innocence is seen when he relays to Scout the story of witnessing Helen Robinson being told by Atticus and Calpurnia that her husband was shot to death while trying to escape from jail. Dill witnessed Helen's very shocking response, a response that's even more traumatic to witness if the observer knows all of the injustices that have led to Robinson's death, as Dill knew. According to Scout, Dill relayed that Helen "just fell down in the dirt. Just fell down in the dirt, like a giant with a big foot just came along and stepped on her" (Ch. 25). What's interesting about Dill's account of Helen's reaction is that neither witnessing her reaction nor telling the story makes Dill cry as it would have done during the trial. Hence, as we see, just as Mr. Raymond predicted, Dill has already lost his innocence, has already become hardened by the atrocities around him.