co-conspirator vs conspirator

co-conspirator

noun
  • A person involved with others in a conspiracy. 

conspirator

noun
  • One of a group that acts in harmony; a person who is part of a conspiracy. 

  • Part of a group that agree to do an unlawful or unethical act. 

How often have the words co-conspirator and conspirator occurred in a corpus of books? (source: Google Ngram Viewer )