Steve Harmon, the protagonist of Walter Dean Myers' Monster, makes a couple huge mistakes which lead him to be accused of murder. First, Steve actually has a conversation with James King about being part of a robbery. King mentions Steve being the lookout and then thinks that he may not be cut out for it.
Steve was at the convenience store that the robbery took place at. While he states that it was a completely different day, other witnesses state that they actually saw him there right before the robbery and murder.
Given that Steve is young, male, African American, and on trial, his lawyer thinks that the jury will look at him like all other young, male, African Americans who end up in prison and on trial. Although this cannot be considered an "action" or "mistake," this does play into his arrest.