A person who assists or protects someone wanted by the police in connection with a crime
some of that atrocious wickedness in Jones, ... might perhaps be derived from the encouragement he had received from this fellow, who ... had been what the law calls an accessary after the fact.
a person who gives assistance or comfort to someone known to be a felon or known to be sought in connection with the commission of a felony
partner after the fact, person who aids a criminal after the latter commits the illegal act (Law)