2.  To convict a criminal defendant, the prosecutor must prove the defendant guilty beyond a reasonable doubt.  As part of this process, the defendant is given an opportunity to present a defense  Most often defendants try to avoid punishment by claiming they did not commit the act in question

3.  What makes a crime a crime? In most cases, an act is a crime because the person committing it intended to do something that the state legislature or Congress has determined is wrong. This mental state is generally referred to as…what?  Mens rea  concept is based on a belief that people should be punished only when they have acted in a way that makes them morally blameworthy

4.  Ordinary" carelessness is not a crime. For example, careless ("negligent") drivers are not usually criminally prosecuted if they cause an accident  more-than-ordinary carelessness ("recklessness" or "criminal negligence") can amount to mens rea.  In general, carelessness can be a crime when a person "recklessly disregards a substantial and unjustifiable risk  People who unintentionally engage in illegal conduct may be morally innocent; this is known as making a "mistake of fact."  Someone who breaks the law because he or she honestly misperceives reality lacks mens rea and should not be charged with or convicted of a crime.  For example, if Paul Smith hits John Jones because he reasonably but mistakenly thought another person was about to hit him, Smith would not have mens rea

5.  Even when people don't realize what they are doing is illegal, if they intentionally commit the act, they are almost always guilty. For example, if Jo sells cocaine believing that it is another legal substance, Jo has made a mistake of fact and lacks mens rea. However, if Jo sells cocaine in the honest but mistaken belief that it is legal to do so, Jo will have mens rea since she intentionally committed the act  Mistake of Law: a person who commits a crime with the firmly-held, but mistaken, belief that the proposed act is permitted will nonetheless be held liable as a criminal.

6. Mistake of Fact or Law?  defendant goes into a supermarket and places eight items in a basket which is presented to the cashier for payment in the usual way. Both honestly believe that all eight items have been scanned, and the defendant pays the sum shown on the bill. A store detective, however, notices that a mistake was made by the cashier so that only seven items were actually priced. This detective arrests the defendant after leaving the store.

7. Mistake of Fact or Law?  if person A was in transit through an airport and picked up a bag which looked like his own, and that bag was to contain a bomb

8. Mistake of Fact or Law?  Person A, the owner of a vehicle, takes it into a garage for repair. When returning to collect it, person A finds that the vehicle has been left parked in the street. If he has an honest belief that he has the right as an owner to retake possession of the vehicle without paying the outstanding bill for the repairs  The belief must be that the law creates and vests a specific right to act in that way

9. Mistake of Fact or Law?  For example, suppose Jennifer is married to John, but decides to get a divorce in order to marry Ben. However, Jennifer mistakenly believes that the divorce was final when she submitted the paperwork required by the state, and did not realize that she had to wait for a court to pronounce her divorced. In the interim, she marries Ben  Jennifer's mistake was not one of governing law (she did not mistakenly believe it was legal to be married to two people  rather a mistake of non-governing law, which is akin to a mistake of fact. Depending on the jurisdiction in which the act took place, Jennifer may be allowed to raise the defense of mistake of law in such a scenario but most likely not.