The mockingbird is an important symbol throughout the novel. It represents innocence and good-heartedness, and Atticus says it’s a sin to kill one. According to Scout, that is the only thing that Atticus labels as a sin. She asks Miss Maudie about it who agrees, saying that mockingbirds never do anything to hurt anybody, they only want to bring joy to others with their singing. In this way the mockingbird symbolises people who are simply and instinctively good and kind, like Tom Robinson and the town recluse, Boo Radley. Tom Robinson’s death, for instance, is compared to ‘the senseless slaughter of songbirds’ (like mockingbirds) by the town editor Mr Underwood.
Scout invokes the mockingbird in relation to Boo Radley at the very close of the novel, after he saves her and Jem from the depraved Bob Ewell who attacked them in the dark. Sherriff Tate declares that he doesn’t want this made public. Boo has proved himself a hero in saving the children, but as Tate realizes, it would be a shame to make him suffer by ‘draggin’ him with his shy ways into the limelight.’ In fact, according to Tate, this would be nothing short of a ‘sin’, bringing such a shy man into the glare of public attention. This is what Scout later comments on. She says to Atticus that ‘Mr Tate was right, and remarks that:’It’d be sort of like shooting a mockingbird, wouldn’t it?'
Scout is agreeing with Tate that Boo would suffer if he was suddenly thrust into the midst of society – the society that has ignored his existence up till now. She realises that society would hurt him, just as it hurt the other innocent, Tom Robinson. People of simple goodness like these two are misunderstood and mistreated by society at large. Scout doesn’t actually mention Boo by name when she makes the remark about the mockingbird, but the reader is meant to understand that she is referring to him through this particular symbol.