A crime under the common law, rather than by statute. Under that doctrine, acts are made criminal by the court if they tend to injure the public and require punishment. Note: under a conspiracy, it is unlawful to agree to commit a crime or to do a legal act in an unlawful manner. It is the making of the agreement, which imports the criminal aspect to even lawful acts. Most of the application of the doctrine of common law crimes involves conspiracies. Most jurisdictions reject the doctrine of common law crimes.