Although it gets gruesome, you have a general background in criminal investigation. Clues such as blood, powder burns, and other various evidence are stimulating. You're trained in techniques for uncovering clues and using information to track down suspects. You may also have criminal informants when combined with Crime. It's all about tracking down answers in the end. This skill is more for knowing the tools of scientific analysis and doesn't replace deductive reasoning.
In ancient settings, a detective rarely had more than his wits and watchful eyes to deduce clues from a scene. Nowadays, criminal forensics has become quite powerful and will greatly aid the investigator in reaching appropriate conclusions.