A person who investigates or conducts inquiries into incidents or crimes; often a member of the police handling on-site inspections and interviews.
現場には数人の捜査員がいて、証拠を慎重に集めていた。
There were several investigators at the scene carefully collecting evidence.
彼女はベテランの捜査員で、複雑な事件の担当経験が多い。
She is a veteran investigator with much experience handling complex cases.
捜査員が目撃者から事情を詳しく聞いている。
An investigator is asking a witness for details.