What do we mean by 'public law' when we say that 'criminal law is public law'? – Public Law and Criminal Law in Australia book forum
Malcolm Thorburn provides the fourth and final post in our book forum on Nicholas Petrie and Julian R Murphy’s edited collection Public Law and Criminal Law in Australia: Overlap, Intersection and Inconsistency. To see all posts, please click here.
22.12.2025
Nicholas Petrie and Julian R. Murphy have done Australia and the world a great service in putting together a terrific volume of essays on Public Law and Criminal Law in Australia. The volume is packed with insights into the myriad complex ways in which public law norms constrain the operations of the criminal law. Its chapters cover the application of public law norms of due process and human rights to such diverse matters as judicial review of criminal proceedings, the application of human rights to independent public prosecutors, privacy and the public interest in whistle-blower legislation. It also includes illuminating discussions of core questions of constitutional law concerning the nature and constitutional limits of punishment and questions of federalism in Australian criminal law.
The book’s success in addressing all these questions is proof that, in one rather loose sense, at least, 'criminal law is public law'. Public law is fundamentally concerned with regulating the exercise of the state’s power over its subjects, and (as Murphy points out in his introductory essay), 'criminal law self-evidently involves the exercise, and regulation, of state power. Indeed, it is in the field of criminal law that one sees the rawest exercise of state power over the subject…' (3). So it should go without saying that the state should abide by basic public law norms of due process, human rights, and the like when exercising its power over its subjects through the criminal law in all the ways that the chapters of this book explore in such rich and illuminating detail. It is in this sense that I have argued (against those who tried to turn criminal law into a relationship between private moral actors) that 'criminal law is public law': it involves the use of state power and should be governed by the norms appropriate to that enterprise.
But there is also a narrower conception of public law into which criminal law does not fit nearly so well. The institutions that are characteristic of that narrower conception of public law really are not only constrained by public law norms of due process, human rights, and the like. What is most important about these areas of public law in this narrower sense is that they are defined entirely by the aspect of the public interest they are designed to promote. Environmental law, the law of public pensions, or the law of highways traffic are public law not only in the sense that they are governed by general norms that constrain the exercise of public power, but also because they are otherwise defined simply in terms of the aspect of the public interest to which they are directed. These core institutions of public law really do operate along the two dimensions that Murphy sets out as characteristic of public law: whether it promotes the dimension of the public and whether it does so in a way that complies with the procedural and formal constraints of public law.
I argue in this short comment that criminal law isnotpublic law in this narrower sense. Unique among the institutions of the modern state, the criminal law is not directed simply at promoting some aspect of the public interest. Rather, its central concern is something conceptually prior to the pursuit of any public interest: namely, vindicating the supremacy of law and the exclusive authority of the state to set the legal terms under which we all shall live. Most of the specific conduct rules that the criminal law enforces are already enforced by some other area of law (tort law in the case of inter-personal wrongs, various forms of public regulation in most other areas). Criminal law is not just a more emphatic way of enforcing the specific rules; it is concerned with the more fundamental relationship of authority that obtains between state and citizen. In this way, criminal law is fundamentally different from all other areas of public law.
Criminal Law and the Public Interest
Once we have recognised that criminal law involves the exercise of public power and that it is therefore subject to public law principles, it is tempting to insist that not only are some criminal law principles just applications of broader public law principles, but that all of them are. This is what we might say about generic areas of public law: the purpose of the area of the law is always some aspect of the public interest, but all of the principles that govern our pursuit of that purpose are just generic public law norms of due process, human rights, and the like. But is criminal law just another area of public law, like environmental law or the distribution of welfare benefits? Julian Murphy seems to be tempted by that thought: he finds it 'puzzling' to find that 'most comprehensive accounts of public law contain no reference at all to criminal law' (3).
As Murphy develops his argument, it seems clear that he wants to show that virtually every criminal law doctrine—not only principles against arbitrariness in punishment or in decisions to prosecute, and procedural requirements of public jury trials, but also substantive principles of subjective mens rea and the development of defences such as duress and provocation—is really just an application of broader public law principles about due process or human rights. If that is so, then, we are tempted to ask what (if anything) makes criminal law special. Murphy seems to have an answer: in criminal law, individual rights seem to play a more important role, and the public interest tends to play a less significant role than it does in the rest of public law. In contrasting criminal offences (which are presumed to take a subjective mens rea) from regulatory offences (that are presumed not to have any mens rea requirement), he writes (at 15): ‘the presumption of mens rea thus provides a striking illustration of the criminal law’s concern dual concern [sic] for the public interest and for the interests of the individual accused.’
Notice the set of assumptions about the nature both of criminal law and of public law that lie behind this picture. It assumes that criminal law is really just an interchangeable part of one undifferentiated field of public law (albeit one where matters of individual rights are more prominent and the public interest less so than elsewhere). In this way, Murphy’s view of criminal law as just a particular individual-rights-intensive flavour of public law is very much in line with a fashionable current in contemporary criminal law theory scholarship according to which criminal law is just another interchangeable part of public law. According to this way of thinking, criminal law is just a particularly harsh, coercive, and ineffectual branch of public law that is almost always less good at bringing about public purposes than myriad public law alternatives: schools and public health measures, licensing regimes and regulatory enforcement.
A number of prominent criminal law theorists such as Vincent Chiao, David Garland, Alice Ristroph, and Bernard Harcourt as well as many economic analysts of criminal justice such as Richard Posner and Gary Becker have promoted this view, insisting that we should think of criminal law as just another generic institution of the regulatory state. If we concede this much, however, it becomes very difficult to explain why we should have a system of criminal justice at all. For by almost any measure, it is an institution that causes enormous suffering while being of questionable value in the pursuit of the public good. If we are interested in effective pursuit of the public good, many of these scholars argue, we should prefer other mechanisms in most cases. David Garland insists that ‘effective, legitimate government must devolve power and share the work of social control with local organizations and communities’ (205). Vincent Chiao point out that states often face a meaningful choice between ‘schools now’ and ‘punishment later’ (229). And Alice Ristroph argues that we should always ask, before resorting to the criminal process, whether ‘some other response—civil law, private ordering, or even doing nothing—would be better than criminal interventions’ (66-67).
As it turns out, however, many of the characteristic doctrines of criminal law are actually quite hard to justify in standard public law terms. If we think of criminal trials and punishment as just generic governance tools, then what principled objections can we mount to the practice of plea bargaining, insisting instead on the importance of public, contested trial by jury, where the prosecution must prove its case beyond a reasonable doubt? If criminal law is just a regulatory tool distributing punishment as a means to inducing greater social cooperation, then what is wrong with the administrators of that system bypassing the slow and costly mechanism of the public jury trial and getting more quickly and efficiently to the distribution of the punishment? The often-expressed worries that criminal punishment too often results from a plea agreement, rather than a public trial, seems to have no purchase unless we insist on the special, public nature of criminal wrongdoing.
Those who see no difference between criminal law and generic institutions of public law have attacked most of the other basic features of traditional criminal law doctrine, as well, on the grounds that they are not required neither by standard public law demands nor by any useful governance purpose. The doctrine of mens rea in criminal law has been under attack from advocates of the governance approach to criminal law for many years. The most prominent and best-known such attack was led by HLA Hart in the 1960s. ‘What is crucial’, Hart argues, ‘is that those whom we punish should have had, when they acted… a fair opportunity to exercise these capacities’. And from this, he concludes that ‘there is no reason… to protest when someone who “just didn’t think” is punished for carelessness’ (152). Following Hart, the rejection of the criminal law’s traditional subjective mens rea standard has become common fare among this sort of ‘public law’ account of the field.
Similarly, we might challenge the requirement of proof beyond a reasonable doubt as being at odds with the pursuit of the public good along the lines of standard public law principles. Perhaps the best-known critic of the traditional criminal ‘beyond a reasonable doubt’ standard is Larry Laudan. If our goal in criminal trials and punishments is to maximise aggregate utility, he argues, then we should adopt a standard of proof that is designed to ensure that we achieve that end. ‘[I]f we could figure out the relative costs to society of false convictions and false acquittals’, he argues, ‘we might be able to use the ratio of those costs as a mechanism for determining the [appropriate standard of proof]’ (68). Even more radically, Federico Picinali has argued for a what he calls ‘justice in-between’, allowing for verdicts somewhere between ‘guilty’ and ‘not guilty’, based on evidence less than proof beyond a reasonable doubt, but also justifying a lesser sanction.
Criminal Law and the Supremacy of Law
If we wish to vindicate these crucial criminal law doctrines of mens rea, proof beyond a reasonable doubt, trial by jury, and so on, our best strategy (I believe) is to recognise that although criminal law is an area of public law in the broadest sense (for it involves the exercise of public power and should therefore be subject to public law norms about its exercise), it is not just another branch of public law like all the others. We should, in short, recognise what some call ‘criminal law exceptionalism’. This is a distinction that historically was captured by the distinction between law and what was (in the seventeenth and eighteenth centuries) referred to as ‘police’.
The police power, as Markus Dubber reminds us, is the origin of the modern administrative state: it is a power to pursue the public interest as seems best to those in charge, subject only to general rule of law principles and certain rights-based constraints. It treats persons as sources of potential threats to the public welfare that can be abated as needed. Thus, ex ante restraint is appropriate, as is the use of coercion that is proportionate not to an individual’s culpability, but to the seriousness of the threat he poses to public welfare. This is the way that we treat the confinement of persons with communicable diseases in quarantine, or of persons suffering from a mental disorder. It is to be contrasted (sharply) with the way we treat persons when we hold them responsible for criminal wrongdoing.
Of course, in the modern regulatory state, public power is often constrained in various ways—giving fair warning to those who might be subject to regulatory penalties (in due diligence defences), imposing proportionality constraints on the use of public power in restraints, and so on. And modern criminal punishment is often treated simply as a means toward bringing about public welfare (through deterrence, rehabilitation, and the like). But the basic logic behind the regulatory state—that we are using power against persons insofar as they are threats to the public welfare and not insofar as they merit punishment for wrongdoing—shows that we are engaged in a very different enterprise in criminal law than we are in the regulatory state more broadly.
Criminal law—in Australia and around the world—is a branch of public law in some very important ways. It is carried out by public actors, it occupies a special place in the constitutional order, and it is subject to public law norms of human rights, fairness, reason-giving, and the like. This wonderful new book draws our attention to all the ways that this connection helps us to make sense of criminal justice institutions in all their complexity. So long as we recognise that it is a distinctive and quite special branch of public law—not merely promoting some aspect of the public interest, but putting in place the structure of legal authority that makes the rest of public law possible—we will also do well to follow Julian Murphy in understanding criminal law as public law.
Malcolm Thorburn is a Professor and the Chair in Law and Innovation at the Henry NR Jackman Faculty of Law, University of Toronto.
Suggested citation: Malcolm Thorburn, ‘What do we mean by 'public law' when we say that 'criminal law is public law'? – Public Law and Criminal Law in Australia book forum’ (22 December 2025) <https://www.auspublaw.org/blog/2025/12/what-do-we-mean-by-public-law-when-we-say-that-criminal-law-is-public-law-public-law-and-criminal-law-in-australia-book-forum>