Another theme in Camus's The Stranger is the conflict between the individuality of experience and the inevitable judgements of others. Meursault's experience is not typical, but instead of being allowed to be unique, he is compared to others.
In part 1, when Meursault is at the funeral, he is aware that his actions are being judged, but he does not feel the same need to judge others. He is indifferent about his neighbor who beats his dog, and he befriends a man who justifies violence against women. There are other peculiarities about Meursault, such as his lack of reaction to his mother's death or his disinterest in typical activities like going to the cinema with his girlfriend.
In part 2, the trial serves as a review of what happened in the first part of the novel. Meursault's accounts of events are different from those of the witnesses at the trial. His justification for not visiting his mother, like his account of the incident with the man on the beach, does not make sense to the other people in the courtroom.
This impossible difference between being-for-itself and being-for-others is also an existential theme of Jean-Paul Sartre's works. Meursault, like all of us, depends on his understanding of other people to inform him about how to act in the world. His unawareness of the perspectives of others is the main problem for him during his trial. He is unprepared when his life is seen differently by others; his identity is something beyond his control, outside of his personal experience.