WASHINGTON (AP) — The text messages captured a cover-up of unimaginable abuse: Parents had struck their toddler so often that they ultimately killed her. The child shook badly because we beat her, the father wrote, and the mother complained that their 2-year-old was the devil.

FBI Director James Comey says encrypting data stored on smartphones and computers could hurt criminal investigations, and evidence reviewed by The Associated Press shows that the child abuse case in Los Angeles from summer 2011 is a powerful, compelling argument. Prosecutors said the texts recovered by investigators prompted the parents to practically beg for a plea deal.