Mens rea is subtly different, I think. It is intended to allow a defense that you really didn't want to break the law and did so unintentionally. It isn't quite about the self-perceived goodness of your intentions. That is, stating "I knew I was breaking the law but my actions were good and I didn't realise people would think I'd done something bad, therefore I don't have mens rea" won't work. Knowledge that it was illegal was sufficient. And mens rea is also not a defense that allows legal ignorance.
It's also worth noting that quite a lot of broad crimes are strict liability these days, especially in America. For example money laundering is a strict liability crime, along with more obvious ones like speeding.
Misconduct though is not normally a criminal law term anyway. More like a code of conduct for an organisation.
Not really. I'm a lawyer so I have a decent grasp of this stuff. Mens rea is closely tied to intent, not really to whether it had anything to do with intending to break a law (ignorance of the law is generally not a defense). Think of the difference between someone who commits premeditated murder, someone who commits manslaughter through gross negligence (e.g., a drunk driver), and someone who by complete accident is responsible for another's death (someone runs out in front of your car). In each case a person's actions directly cause another person's death, however we attach different levels of culpability to each. We're getting a little bit far afield from original issue, here, though. Anyway . . .
It's also worth noting that quite a lot of broad crimes are strict liability these days, especially in America. For example money laundering is a strict liability crime, along with more obvious ones like speeding.
Misconduct though is not normally a criminal law term anyway. More like a code of conduct for an organisation.