Accusing, condemning, and avenging are part of our daily life. However, a review of many years of literature attempting to analyze our blaming practices suggests that we do not understand very well what we are doing when we judge people culpable for a wrong they have committed. Of course, everyone agrees that, for example, someone deserves censure and punishment when she is guilty of a wrong, and the law has traditionally looked for a mens rea, or “guilty mind,” in order to convict someone of a criminal wrongdoing. But philosophers and legal theorists have found it interestingly difficult to say what mens rea is. For example, noting the way in which we intuitively think people aren't culpable for a crime if they disobey the law by mistake, or under duress, or while insane, theorists such as H.L.A. Hart have tried to define mens rea negatively, as that which an agent has if he is not in what we consider to be an excusing state. But such an approach only circumscribes and does not unravel the central mystery; it also fails to explain why the law recognizes any excusing states as mitigating or absolving one of guilt, much less why all and only the excusing states that are recognized by the law are the right ones. Moreover, the Model Penal Code, which gives a very detailed account of the kinds of mental states which justify criminal conviction, does not tell us (nor was it designed to tell us) why these states of mind (e.g., knowledge, purposiveness, intention, assumption of risk of harm, negligence) are relevant to an assessment of legal guilt.
The Sentencing Guidelines as a Not-so-Model Penal Code