1·Plain clothes policeman who work undercover to detect crime.
隐蔽调查犯罪的便衣警察。
2·We pledge to uphold the law, to protect life and property, to prevent and detect crime.
我们承诺维护法律，保护生命和财产，防止和侦查罪案。
3·Undercover Investigations is a useful method to detect the organized crime and group crime.
卧底侦查是侦破有组织犯罪、团伙犯罪等案件的有效手段。