Criminals leave fingerprints, but also traces of what they feel, how they attack, and who they choose. This idea inspired, in the 1970s, a new method at the FBI to understand how the most feared criminals in US prisons thought, as recalled in the acclaimed Netflix series. MindhunterSince then, police investigations have never been the same. Behavior analysis deduces how an unknown offender will act based on the behavior they exhibit during a crime, and since its inception, this discipline has gained ground among elite teams and the most prestigious police forces around the world. Its essence: putting a magnifying glass on the motivations of attackers. "Historically, the police have been primarily concerned with the what, the how, the when, the who, and the where; but we left out the why," says Xavier Álvarez, the first behavioral analyst for the Mossos d'Esquadra (Catalan police). A question that often connects the victim with the perpetrator.