California Penal Code section 182 makes it a crime to even "Conspire" to commit a crime. Thus, even if you didn't actually commit the underlying offense, you can still be convicted of conspiring to commit it. To be convicted under Penal Code 182, the district attorney must prove that one or more individuals conspired to commit a crime.
A conspiracy is an agreement between two or more parties to commit a particular crime. In order to be found guilty of a conspiracy, the DA must prove the following elements.
1. There was an agreement between two parties. An express agreement need not be proven. Rather it can be proven by circumstantial evidence showing a common intent, plan or scheme indicating an agreement.
2. You knew the act was illegal. Because conspiracy is a specific act you must know that act agreed upon is illegal or is a crime. If you agree to transport a white powdery substance which turns out to me cocaine you may be charged with conspiracy to transport a controlled substances. However the District attorney must prove that you knew the substance was illegal and you still intend to transport it.
3. You committed an overt act in furtherance of the agreement. Simple agreeing to commit a crime is not enough. An overt act means any step taken, or any act committed which goes beyond mere planning and agreement, which furthers the objective of the conspiracy. The overt act in and of itself does not necessarily have to be illegal.
The punishment for conspiracy varies depending on the underlying crime. However, for most general types of crimes, the punishment would be the same as if you had personally committed the crime.
Because conspiracy is a specific intent crime, there are many defenses available to an individual facing conspiracy charges. The fact that there was no actual agreement, that you didn't know the act was illegal, or that no overt act occurred in furtherance of the conspiracy are all valid defense. Further, an open and voluntarily withdraw from the conspiracy before any overt act occurs will be a valid defense to the charge of conspiracy.
Conspiracy laws can be confusing because of so many intricacies and the specific intent elements. If you are charged with conspiring to commit a crime, contact an attorney immediately. They will be able to determine the best approach for attacking and hopefully absolving you of those charges.