Conspiracy is an agreement involving two or more persons to commit an illegal act or to perform a legal act unlawfully. Under federal law the general conspiracy provision has a maximum sentence of five years imprisonment. However, there are a number of conspiracy provisions particular to certain categories of crime (i.e., drugs, fraud) in which the penalty provisions are the same as for the substantive crimes. States also have conspiracy provisions. In most states the penalties for conspiracy are lower than for the substantive criminal offenses.

The law of evidence involved in proving conspiracy has a number of nuances. A person charged with conspiracy needs the aid of an attorney very experienced in both the substantive area of criminal law and representing individuals charged with conspiracy.