Lucia de Berk was known for volunteering to work difficult shifts with the most critically ill patients — a pattern that independent nursing experts recognized as a mark of professional dedication. Once she was identified as a suspect, investigators and prosecutors reinterpreted this same behavioral pattern as evidence of pathological motivation. What specific psychological profile — borrowed from the nursing literature — did investigators apply to her, and what is the evidentiary problem with diagnosing a behavioral profile from the same data used to establish guilt?