In My Soul to Keep, at what point do you realize that Jessica's relationship with her husband is not ideal?

Even before David starts to tell Jessica about his immortality, she has already noticed the strange way that he heals abnormally quickly. It is not until she is interrogated by Lieutenant Reyes that Jessica begins to be suspicious that her husband might be a murderer. After her sister is injured in an accident in which she says she was pushed from her balcony, Jessica suspects that her husband was the one to hurt her sister. She finally looks at the composite sketch of the alleged killer of Rosalie Banks, David's daughter from another marriage and realizes that it was David who killed Rosalie.