cold case
noun [ C ] uk/ˌkəʊld ˈkeɪs/ us/ˌkoʊld ˈkeɪs/
（未解决的）冷案，悬案
a case (= a series of events investigated by the police) that has not been solved
The Police Department began using interns last September to take a fresh look at old, unsolved murder cases, also known as cold cases. 去年九月，警察局开始使用实习生来重新审视那些陈年未破的谋杀案，也就是所谓的悬案。
A cold case unit was formed specifically to review and reinvestigate all of the department's unsolved killings, according to police. 警方表示，已经成立了一个悬案小组，专门审查和重新调查该部门所有未解决的谋杀案件。
- More examples
- More than six years after the murder, the homicide unit's cold case squad is reinvestigating the case.
- We're reopening this cold case, based on this information, and will be doing follow-up interviews as soon as possible.
- Law enforcement agencies in Washington and across the country rely on DNA databases to help solve so-called cold cases.