In short, it is both. Meursault has shot a man in cold blood for no significant reason at all. This is why he is brought to trial. However, as the trial progresses and the evidence is brought out, the judge and jury become more perplexed by Meursault's strangeness in general. Most murders are committed for reasons, whether it be hatred or jealousy, money or some other form of gain, yet Meursault killed the Arab because the sun was in his eyes. One might think this is enough reason to convict Meursault or at least conclude he is insane.
The prosecutor starts attacking Meursault for his indifference towards his mother's death, an event which has nothing to do with the murder but helps to turn everyone in the courtroom against Meursault. The others view Meursault as cold, even monstrous and evil, because he went to the movies with his girlfriend so shortly after his mother's funeral. His antipathy towards social obligations seems to shock them all more than an act of violence.
(The entire section contains 3 answers and 873 words.)