capital punishment vs first-degree murder

capital punishment

noun
  • The practice of putting a person to death as a punishment for a crime. 

first-degree murder

noun
  • An act that constitutes the crime of first-degree murder. 

  • The criminal offence of murder in a form considered by law to be the most serious; the precise distinction may vary by jurisdiction but typically involves premeditation, or the choice of victim or other circumstances being regarded as especially blameworthy. 

How often have the words capital punishment and first-degree murder occurred in a corpus of books? (source: Google Ngram Viewer )