What are three quotes from To Kill a Mockingbird that reflect on the loss of innocence?

Mr. Gilmer's cross-examination of Tom Robinson is Dill's moment, Jem's is the guilty verdict, and Scout's is Mr. Ewell's attempt to kill her and Jem.

Since this is a coming of age story, loss of innocence is a theme that threads its way through.  Many of the children’s innocence-impaling experiences involve the Tom Robinson trial.  They are young, and they are just learning that the world is not fair.

One of the most profound examples of this is Dill’s reaction to Tom Robinson’s trial.  Dill, like many kids, is young and naïve.  He doesn’t quite know how the world works.  He has a physical reaction to the trial.  Mr. Gilmer’s racist and degrading cross-examination of Tom Robinson makes him vomit.

“That old Mr. Gilmer doin‘ him thataway, talking so hateful to him—”

“Dill, that’s his job. Why, if we didn’t have prosecutors—well, we couldn’t have defense attorneys, I reckon.”

Dill exhaled patiently. “I know all that, Scout. It was the way he said it made me sick, plain sick.” (Ch. 19) 

Dill can’t tolerate Mr. Gilmer’s behavior.  Dolphus Raymond sees him get sick and gives him some Coca-cola.  He tells Dill he is not “thin-hided.”  It should make him sick.  Scout doesn’t see what Dill sees, and Jem hasn’t really caught on yet either.  He is still idealistic, while Scout is pragmatic.  Dill has just gotten a lesson in racism so profound that it literally turned his insides. 

That brings us to Jem’s loss of innocence.  Despite Mr. Gilmer's performance and Dill’s reaction to it, Jem holds out hope that Tom Robinson will be acquitted.  From a legal standpoint, he is pretty sure that everything will be fine.  He thinks that Atticus has made his case.  Then he hears the verdict. 

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. (Ch. 21) 

To Jem, the verdict is a betrayal.  He never really understood until that point how deep racism really went.  It went beyond treating someone disrespectfully and calling a grown man “boy.”  It meant that a black man could not get a fair trial, even when all of Maycomb thought he was innocent.

That leaves Scout.  Scout is the youngest of the three children and the protagonist.  While the trial is important to her, her childhood seems to center around Boo Radley.  Scout was pretty young when Bob Ewell attacked her.  She was already growing up quickly because of the trial, but from that moment you can’t really say she was a child any more.  When someone tries to kill you, you have lost your innocence.

“Anyway, Jem hollered and I didn’t hear him any more an‘ the next thing—Mr. Ewell was tryin’ to squeeze me to death, I reckon… then somebody yanked Mr. Ewell down. Jem must have got up, I guess. That’s all I know…” (Ch. 29)

Scout’s childhood comes full circle when Boo Radley saves her life.  She realizes fully that things are not always what they seem, and people are more than their reputation.  Boo Radley is not the scary monster of her childhood.  He is a friend.  Racism and other scary and terrible things may exist, but there are also people looking out for you.