捜査

This term is used exclusively for official investigations conducted by law enforcement agencies, such as the police or prosecutors, specifically to solve a crime or identify a suspect. It carries a strong connotation of legal authority and formal procedure.

It is critical to distinguish "sōsa" (捜査) from "chōsa" (調査). While both can be translated as "investigation" or "survey," "chōsa" is a general term used for research, market surveys, or academic inquiries (e.g., a population survey or a scientific study). Using "sōsa" for a non-criminal research project would be a significant error, as it implies a criminal investigation.

Additionally, it differs from "sōsaku" (捜索), which refers to the physical act of searching for a missing person or a hidden object (a "search"). "Sōsa" encompasses the entire strategic process of solving a crime, including interviewing witnesses, analyzing evidence, and tracking suspects, whereas "sōsaku" is the specific act of looking for something in a physical space.