first-degree murder vs second-degree murder

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. 

second-degree murder

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

  • The criminal offence of murder in a form defined as less serious than first-degree murder; the precise distinction may vary by jurisdiction but typically involves second-degree murder being intentional but not premeditated. 

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