In order to prove criminal conspiracy charges, prosecutors in California must be able to convince juries that defendants entered into an arrangement to commit a crime, intended to commit that crime and took action to move the plan forward. Defendants can be convicted of conspiracy even if the crime they planned is never committed and the overt act taken to complete the scheme was not a criminal act.
For example, purchasing ski masks is completely legal, but purchasing ski masks to wear during an armed robbery would be considered an overt act in a criminal conspiracy prosecution. The overt act requirement exists to prevent individuals from being sent to jail for just talking about committing a crime during a lively conversation. Proving that a plan existed and one of the parties involved took action in pursuit of it is often fairly straightforward for prosecutors, but establishing intent can be very challenging in these cases.
Criminal conspiracy is what is known as a specific intent crime. This means that prosecutors must be able to prove beyond any reasonable doubt that the alleged conspirators truly intended to go through with the scheme. Such proof may be established by showing that a series of overt acts were taken, but it is more commonly established when one of the defendants pleads guilty and agrees to testify against the other conspirators.
Crimes that hinge on intent can be very difficult to prove. Therefore, experienced criminal defense attorneys may be reluctant to resolve conspiracy cases at the negotiating table unless the evidence against their clients is extremely compelling or the prosecutor involved makes a very generous offer. When arguing these cases in court, defense attorneys could try to plant seeds of doubt about the existence of the plan, the intent to carry it out and the overt act or acts taken in furtherance of it.