Why does Justine Moritz die?

Justine dies because Victor knows who killed William and says nothing. The creature plants evidence; the court believes a servant’s guilt because it is convenient; Justine, under religious pressure, confesses to a crime she did not commit. Victor’s silence is the creation-and-abandonment problem in public form: telling the truth would expose his secret and sound insane, so an innocent woman is executed to protect his credibility.

The episode stops the novel from being only a private revenge tragedy. Family affection — the Frankensteins’ kindness to Justine — cannot survive a knowledge that will not enter the courtroom. Readers looking for “who is the real monster” should sit with this chapter before they answer. The creature murders; Victor’s withheld speech makes the law finish the work.