queen's evidence

noun

1. （刑事被告向法庭提供的）对同案犯不利的证据
   if a criminal turns Queen's evidence , he or she gives evidence against the people who committed a crime with him or her

1. That fellow that turned queen's evidence on the invincibles he used to receive the, Carey was his name, the communion every morning.
   那个向政府告密、背叛常胜军的家伙，他叫凯里，每天早晨都来领圣体。