When does Camus mention chance and luck in this chapter? Why do you think he includes these concepts here? What is their significance?

The defense does little to help Meursault's case because his witnesses, like he himself, can give little reason to justify Meursault's actions besides comments which are immediately thrown out such as Céleste's idea of bad luck and Raymond saying it was all just chance. But did chance or bad luck cause him to shoot the man five times? This idea is also ridiculous, so that neither side of the case can truly be taken seriously by the reader. He is not on trial for his real crime but for his moral character and his defense can offer no redeeming testimony.