in cold blood vs poker face

in cold blood

prep
  • In a ruthless and unfeeling manner, particularly as applied to first-degree murder committed without provocation and with malice aforethought. 

poker face

noun
  • Any similar expression used to prevent giving away one's motives, feelings, or situation. 

  • An impassive facial expression cultivated to prevent other players from determining whether one's actions in the game are the result of a quality hand, or of bluffing. 

How often have the words in cold blood and poker face occurred in a corpus of books? (source: Google Ngram Viewer )