Comparative Insight — Mens Rea

Taylor Dunkley
6 min readOct 7, 2020


The three resources for this week’s module focus on the element of mens rea and offer differing perspectives and insights. As mentioned during a previous class discussion, there are typically multiple elements or features necessary for something to be considered a crime. (Perhaps something like: a crime = an act + a mental state + a circumstance + causation.) Mens rea is typically defined as a certain mental state that makes one culpable, ranging from something as minimal as negligence to something as major as intent, with recklessness and knowledge without intent in between.

The podcast from Hi-Phi Nation begins with a discussion on “governing through crime” and strict liability laws where no mens rea is required and where accidents and ignorance of the law is no excuse (Ignorantia juris non excusat). In these types of crimes, mens rea does not need to be proven, only actus reus needs to be proven. As the members of the podcast point out, mens rea requirements prevent people from being punished for bad things that happen when there is no proof of some type of bad mental state. In other words, mens rea requirements ensure that someone does not get punished for simply doing a wrong thing, but rather only for doing a wrong thing without excuse. When mens rea requirements are dissolved, actions bypass the hierarchy (outlined above) altogether.

The podcast discusses why mens rea and the distinctions between different types of mens rea may be of such great importance to us — it suggests that subtle psychological differences intuitively make huge differences to us. As one of the podcast guests put it, “The way a person values their interests compared to the interests of others” is fundamental to how we view the nature of their actions. But then, of course, the question becomes whether we should be policing the attitudes/thoughts of different people whose actions are otherwise equally wrong. The judgments we make about mens rea and its role as an element of crime also affect strict liability crimes, white collar crimes, and corporations. All of these were subjects of great debate in 2016 when some members of Congress attempted, but failed, to pass a criminal justice reform bill.

Towards the end of the podcast, William Blackstone’s principle that it is better to let ten guilty people go free than to let an innocent person suffer is discussed. This is of significant importance not only to the topics within the podcast, but also to Gideon Yaffe’s article, Mens Rea by the Numbers. What Blackstone’s comment implies is that there needs to be a very high standard of proof in order to convict someone of a crime, something like “proof beyond reasonable doubt.” Although Blackstone was an English jurist in the 18th century, it appears that his principle has been adopted, at least in spirit, by the American judicial system, where there is a high standard of proof and where it is viewed as better to let the guilty go free than to let the innocent be punished. Alternatively, some have taken the principle and turned it almost into an actual formula or ratio that ought to be applied within the criminal justice system.

Moving on to Yaffe’s piece, there is an initial discussion on the bipartisan legislation that attempted to reform criminal justice and install a default mens rea provision, as discussed in the Hi-Phi Nation podcast. Yaffe’s goal is to argue in favor of the default mens rea provision proposed by Congress, which would mean that “statutes silent on mens rea, that were not explicitly identified as strict liability by the legislature, would be taken to require for guilt proof of knowledge with respect to each material element” (394–395). However, Yaffe argues against the “numerical argument” used by many on both sides of the debate to either support or oppose the default mens rea provision. The numerical argument, which literally applies “Blackstone’s ratio,” is something that Yaffe provides refutations for, although his points still remain rather confusing to fully grasp.

What seems to be clear, however, is that one of Yaffe’s problems with the numerical argument is that it considers the number of “hits” and “misses” of convictions and acquittals in a very consequentialist/utilitarian way, where what is “good” is equated with what is “right.” From a deontological perspective, what is “right” does not depend simply on the consequences or the maximization of utility for the greatest number of people, and Yaffe chooses to adopt a deontological perspective and combine it with a somewhat utilitarian “threshold.” Together, this essentially states, “make the world as good as it can be, so long as you do not convict without mens rea, unless you make the world a much, much better place than you could otherwise” (403). In the end, Yaffe defends the default mens rea provision, but discards the numerical argument as a defense of it. To Yaffe, the only things that should be exceptions to the default mens rea provision (and therefore should be classified as strict liability) are: 1) sex crimes against children, and 2) behaviors that are more wrong when acquitted (407).

Lastly, there is Marcia Baron’s Mens Rea, and What We Want the Element of Mens Rea to Provide. In this piece, Baron questions the definition of mens rea — she thinks it is misleading to equate it to a “mental state” as it is commonly defined — as well as the inclusion of negligence in the categories of mens rea, asking whether negligence is sufficient for criminal liability. Using definitions from the Model Penal Code (MPC), she emphasizes the distinctions between negligence and recklessness. Whereas negligence involves “failure to perceive” risk and “gross deviation from the standard of care,” recklessness entails someone “consciously disregarding” known risk in a “gross deviation from the standard of conduct” (70–71). Of course, here, questions arise about what does it mean to be unaware of risk? Is “forgetting” or “failing to notice” something over which one has no control (77)? What if it is agreed upon that one does have control over what one remembers or notices? Even so, Baron suggests that the action is still lacking what mens rea requires — an inculpatory factor (something that adds to the action). The fact that one can control what they remember or notice means that they do not have an excuse (something that takes away from the action). In this rendering of things, negligence does not seem to be an element of mens rea.

However, that depends on one’s definition of mens rea — the lenient sense vs. the strict sense. The lenient sense of mens rea says that someone is not culpable unless there’s an inculpating factor (addition). The strict sense of mens rea says that someone is culpable unless there’s an excusing factor (absence). The Hi-Phi Nation podcast seems to define mens rea (although not explicitly) more in line with the strict sense of the term (82). After a discussion of the differences between whether mens rea should be conduct-based or based on something like “belief formation,” Baron does not seem convinced either way. In closing, Baron concludes that there are many questions and debates about mens rea in general and negligence in particular that she did not necessarily answer or solve, but she hopes her piece will make readers think more deeply about these things and will encourage them to engage in further discussion on the mater, which it certainly has(88).

As is evident from the short summaries of this week’s readings provided here, all three are interrelated (and could be further interrelated with readings from previous weeks) in so far as they discuss mens rea and its elements and contribute to answering the module question of what features something must have before we could permissibly criminalize it.



Baron, M. (2019). Negligence, Mens Rea, and What We Want the Element of Mens Rea to Provide. Criminal Law and Philosophy, 14:69–89. Retrieved October 6, 2020, from

Hi-Phi Nation. (2020). Criminal Minds. Hi-Phi Nation. S4:E1.

Yaffe, G. (2017). Mens Rea by the Numbers. Criminal Law and Philosophy, 12:393–409. Retrieved October 6, 2020, from