In a conversation between Philip Lombard and Vera Claythorne in Chapter 10 of the novel, Philip explains why he thinks Justice Wargrave is the killer on the island. Philip gives his reason in these words: "He [Justice Wargrave] gets to see himself as all-powerful, as holding the power of life and death- and it's possible that his brain might snap and he might want to go one step further and be Executioner and Judge Extraordinary."