This is an interesting question, and one that I would answer by refering to the end of the story and the eventual fate of Mr. Harvey. The message of the story concerning justice seems to be that your crimes will catch up with you, and that you cannot outrun justice, even if you do not receive justice at the hands of law and order. Mr. Harvey is a perfect case in point. Having managed to commit the apparently perfect crime and then to carry on living next door to the girl he murdered, he evades every attempt of the police or of Susie's father to accuse him of the murder. It is only when Susie's sister actually breaks into the house and enters it that suspicions are raised, but he is able to find enough time to flee. As we come to the end of the story, we are left with the nagging thought that justice will not catch up with him and he will be free to murder again as he murdered Susie and so many others before. As he engages another girl in conversation and plans another rape and murder, Susie watches as his plan turns out somewhat differently than he expected:
A moment later, the icicle fell. The heavy coldness of it threw him off balance just enough for him to stumble and pitch forward. It would be weeks before the snow in the ravine melted enough to uncover him.
This is the major technique that is used to present the novel's theme of justice, which cannot be outran or evaded. Even though he is not arrested, Mr. Harvey faces the justice of nature for what he has done.