informer

• One who informs against others ; an informer
  告密者检举他人的人；告密的人
• Any one of our employees could be the informer
  我们的任何一位雇员都有可能成为告密者。
• Why did you do it ? - he was an informer
  你为什么要那么做？ -他是个线人
• - why did you do it ? - he was an informer
  -你为什么要那么做？ -他是个线人
• " grass " is a criminal slang for " informer "
  Grass是罪犯用的俚语，意思是“告密的人” 。
• The government refused to disclose the names of the informers
  政府拒绝透露告密者的姓名。
• On informers of the police in the process of criminal jurisdiction
  论刑事司法中的警方线人
• An approach to police informers ' right of refusing to give evidences
  警方线人拒绝作证权初探
• On informer of police and its legal regulation
  警方线人及其法律规制
• An informer denounced him to the police ( as a terrorist )
  检举人已向警方告发他（是恐怖分子）