What is conspiracy in law?

The elements

• An agreement between at least two people, which can be inferred from conduct — nothing needs to be written or spoken outright.
• Intent to agree and intent that the object offence be committed.
• An overt act by any conspirator in furtherance of the plan, required by federal law for most conspiracies and by many states.

Why prosecutors like it

Three practical advantages. Liability reaches people who never touched the offence itself. Under the Pinkerton rule in federal court, each conspirator can be liable for foreseeable crimes committed by the others in furtherance of the plan. And statements by one conspirator made during and in furtherance of the conspiracy are admissible against all of them, as an exception to the hearsay rule.

Defences

No agreement — mere presence, knowledge or association is not enough. Withdrawal, which requires an affirmative act communicating abandonment to the others or a disclosure to law enforcement, and which must come before the overt act to defeat liability entirely. Impossibility is generally not a defence. Neither is the acquittal of a co-conspirator in most modern jurisdictions.

Penalties

Under federal law the general conspiracy statute carries up to five years, but many specific conspiracies — drugs, fraud, racketeering — carry the same penalty as the completed offence. Sentences for the conspiracy and the substantive crime can be imposed separately.