free pass vs impunity

free pass

noun
  • An exemption from normal processes. 

  • An intentional walk. 

  • A document entitling the bearer to free transportation. 

impunity

noun
  • Exemption from punishment. 

  • Freedom from punishment or retribution; security from any reprisal or injurious consequences of an action, behaviour etc. 

How often have the words free pass and impunity occurred in a corpus of books? (source: Google Ngram Viewer )