Can someone give me an example of when mistake of law would negate the mens rea needed for an offense. This would be a defense under MPC.
There are three main exceptions to the common law rule that there is no defense for mistake of law.
1. Reasonable reliance on an official statement or interpretation of the law
2. Under the Lambert Principle: Lambert states that a D. can make a mistake of law defense to certain statutes on a constitutional basis. The court ruled the there is a constitutional requirement of knowledge for certain types of statutes. There are three factors to determine whether a statute qualifies under lambert: a) the statute is a status offense b) the statute is an omission offense and c) the statute is a malum prohibitum rather than a malum per se. In order to allow for a mistake of law defense, the statute will most likely need to meet all three elements.
3. For specific intent crimes (not strict liability or general intent crimes), if D. committed the offense based on his ignorance of the existence of a different law
, he may be allowed a mistake-of-different-law defense.
The MPC basically follows these same rules. The biggest difference is that the MPC does not use the Lambert principle (it was written before Lambert). In its place, the MPC uses the standard of statutes that are unpublished and therefore not capable becoming known through investigation into the law. The big difference between this and Lambert is that Lambert will apply to certain statutes that are nonetheless published. In this sense, the MPC is slightly more strict than the common law.