Can people be committed for crimes they didn't even know existed?
I've practiced law for almost 38 years, with most of this time devoted to criminal law, either as a federal prosecutor or a white collar defense attorney. Through these years I've witnessed certain trends within criminal law that are both disturbing and seemingly inexorable. Two in particular should give us the most pause: the erosion of mens rea, and the perversion of respondeat superior.
The bedrock principle of Anglo-American criminal law has always been that people must know they are doing something wrong before they can be found guilty and branded a criminal. This legal concept is known as mens rea, Latin for "guilty mind." The reason for this fundamental legal requirement is obvious: violations of criminal laws are serious, and before we put a fellow citizen in jail, we want to make certain that he is actually a bad person, is morally culpable for his crime, and that he deserves to go to jail. Indeed, the Supreme Court's recent decision overturning mandatory life sentences for juveniles partially reflects this idea. Meting out harsh punishment to those who don't even truly understand the import of their actions offends our very notion of justice.
There are of course worthwhile exceptions to this principle (statutory rape is one), and we certainly don't want to reward those wrongdoers whose minds are "innocent" merely because they are willfully ignorant of what the law requires. But generally speaking, we want to make certain that people not only in fact did what they are accused of doing but also that they did so with a guilty mind -- that they actually intended to do something wrong.