On chapter 8 of Mary Shelley’s Frankenstein, Justine Moritz is accused of murdering little William Frankenstein. William is Victor’s young brother and, by default, Elizabeth’s cousin (although she explains that she feels as if he were her brother as well).
Justine had no alibi. In fact, the night of the murder she was given time off. She then went to visit an aunt in a nearby village. Therefore, nobody could have known exactly what Justine was doing that night. However, the one piece of evidence that Justine could not explain in order to proof her innocence was how the child’s locket ended up in her possession. Justine had placed a locket with a picture on William’s neck hours before he went missing. The fact that she had it in her possession after his death had occurred made the jury conclude that Justine must have been near the dead body. Yet, not even Justine could explain this occurrence and begged the jury to consider her character and the flawless way in which she has always lived her life as proof that she would be incapable of doing such a thing.
The strongest evidence against Justine was William’s locket that was found in her possession. She also had no alibi to corroborate her whereabouts on the day and at the time of the murder. Victor knew she was innocent, but he was afraid of telling the truth because it involved exposing the monster that he created. Justine was found guilty and executed for a crime she did not commit.
Victor learned of Justine’s innocence after the monster narrated to him his experiences after Victor abandoned him. The monster told Victor of how he came across a boy (William) and thought of making him his companion. He hoped the boy would be innocent enough to ignore his appearance but instead, the boy fought him spiritedly, and the monster ended up choking him to death. He took William's locket and planted it on a girl he found sleeping in a barn, and that was how Justine was found in possession of the jewelry.
The crime had its source in her: be hers the punishment! Thanks to the lessons of Felix and the sanguinary laws of man, I had learned now to work mischief. I bent over her, and placed the portrait securely in one of the folds of her dress.