How did the detective's reasoning come from?

This is a comprehensive knowledge, which is based on environmental evidence, witness testimony, criminal psychological profile, logical deduction, criminal records, professional opinions of forensic doctors and forensic personnel, and the experience, thinking ability and actions of case handlers. Among them, environmental evidence includes background, murder scene and physical evidence. In addition, each detective's handling method and reasoning method are not necessarily the same. If LZ wants to know more, he can read more mystery novels or related professional books, such as criminal psychology, behavioral psychology, blood type, genetics and so on. I also watch some TV dramas and movies about criminal investigation.