Civil conspiracy requires an agreement between two or more persons to accomplish an unlawful purpose, or a lawful purpose by unlawful means, together with an overt act causing damage.
No independent tort. In nearly every jurisdiction, conspiracy is not itself actionable — there must be an underlying wrong. If the substantive claim fails, the conspiracy claim fails with it. Pleading conspiracy to breach a contract generally fails for this reason.
Why plead it. It extends liability to participants who did not commit the underlying act, permits joint and several liability, may reach individuals behind an entity, and can affect limitations and venue.
The intracorporate conspiracy doctrine holds that a corporation cannot conspire with its own officers acting within the scope of their employment, because the entity and its agents are a single actor. Exceptions exist where the agent acts for personal benefit outside the scope of employment.
Proof. Direct evidence of agreement is rare; it is usually inferred from parallel conduct, opportunity, relationships and communications. Mere parallel conduct without more is insufficient.
Pleading standards. Where the underlying wrong is fraud, the particularity requirement extends to the conspiracy allegations, and conclusory assertions that defendants acted in concert are dismissed.