An investigator (typically of the police); a person belonging to a law-enforcement or investigative agency who carries out crime scene examinations, interviews, and evidence collection.
捜査官が現場で証拠を慎重に調べている。
Investigators are carefully examining the evidence at the scene.
その事件は捜査官によって再び調査された。
The case was re-investigated by investigators.
捜査官は容疑者に事情聴取を行った。
The investigator questioned the suspect.