Stuart Green is a leading exponent of criminal law's special part (i.e. that which constructs specific crimes). In particular, he has published numerous books addressing questions of criminalisation within distinct offence categories. As well as his co-edited collection with Antony Duff on Defining Crimes: Essays on the Special Part of the Criminal Law (Oxford 2005), he has examined white-collar wrongdoing in Lying, Cheating, and Stealing: A Moral Theory of White-Collar Crime (Oxford 2006) and the law of theft in Thirteen Ways to Steal a Bicycle: Theft Law in the Information Age (Cambridge, MA 2012). Additionally, he has begun research on a new book evaluating homicide law. That project will follow his latest monograph, Criminalizing Sex: A Unified Liberal Theory (Oxford 2020), which is perhaps his most ambitious book to date – and one which sets the bar high for its successor.

In Criminalizing Sex, Green investigates the conceptual underpinnings, both moral and legal, of a divergence in the law of sexual offences, including the coherence of those underpinnings and whether they require reconstruction of such offences. He begins by explaining this divergence (pp. xiii–xvi). Ultimately, criminal law has become more punitive in respect of sexual conduct that is non-consensual: this is evident from the expansion of crimes like rape and sexual assault, along with the creation of offences targeting sex trafficking, child grooming, sexual transmission of disease, female genital mutilation and forms of online, image-based sexual abuse (e.g. revenge porn). Accompanying, and sometimes driving, these developments has been a shift in public attitudes regarding what constitutes non-consensual sexual behaviour (see the #MeToo movement), something which continues to evolve. Simultaneously, though, criminal law has also become more permissive – again, reflecting changes in social mores – via the legalising or decriminalising of consensual activity such as fornication, adultery, homosexuality, miscegenation, as well as the production and possession of adult pornography.

Of course, this permissiveness is absent in some countries, notably much of the Muslim world, but Green's focus is the West. And it is this comparative dimension which first hints at the scale of his “unified” analysis (pp. xvii, 44) – one where he assimilates a mass of doctrinal and empirical information on sexual offences in various jurisdictions, together with relevant academic literature, to help make sense of those offences. The second hint of that scale comes from his inclusion in the book of all sexual offences (non-consensual, consensual and aconsensual), this entailing discussion of a multiplicity of behaviour. He often grounds study of that behaviour, and its legal implications, in separate disciplines – drawing on a swathe of insights from, for instance, criminology, psychiatry, psychology, sociology and theology. Meanwhile, his analysis is “liberal” in that it emphasises personal autonomy and rights, alongside the prevention and censuring of conduct which is harmful and wrongful (pp. xvii, 38–51). This framework, anchored in the writings of figures like Mill, Hart and Feinberg, remains a popular paradigm in criminal-law theory, albeit that sexual offences remain apt for enquiry through several alternative – such as feminist or queer – perspectives.

Green divides the book into four parts. Part I explores the meaning of key concepts. Here, he defines “sexual offence” and “sexual conduct” (Chapter 1); “autonomy” and “consent” (Chapter 2); together with “criminalisation” and “liberalism” (Chapter 3). Next, Part II delves into non-consensual and unwanted sex through use of four subparts: II.A looks at proving non-consent in rape, dealing with rape law commonalities (Chapter 4), rape as non-consensual sex (Chapter 5), rape by deceit (Chapter 6) and rape by coercion (Chapter 7); II.B assesses presumptions of non-consent across incapacity (Chapter 8), statutory rape (Chapter 9) and abuse of position (Chapter 10); II.C attends to unwanted sex, specifically sexual harassment (Chapter 11); and II.D scrutinises assumptions of risk inherent in voyeurism (Chapter 12) and indecent exposure (Chapter 13). Subsequently, Part III tracks putatively consensual sex, namely incest (Chapter 14), sadomasochistic assault (Chapter 15) and prostitution (Chapter 16). Finally, Part IV considers aconsensual sex, reviewing bestiality (Chapter 17) and necrophilia (Chapter 18).

Accordingly, the monograph covers a vast amount of sexual-offences terrain, although even then, as Green admits (p. xviii), it cannot cover everything. He omits to cover historical offences like sodomy, abortion and possession of adult pornography; he says little about sexual crimes involving children (e.g. grooming), apart from in relation to statutory rape and incest; unsurprisingly, for an author critiquing substantive criminal law, he ignores procedural factors relating to investigation, prosecution and punishment, including the disciplinary processes for dealing with sexual misconduct on university campuses; and he is silent on the sexual abuse of LGBTQ+ persons, or about how race, ethnicity or socio-economic status impact rates of sexual offending, victimisation, prosecution or punishment. However, notwithstanding these exclusions, the book presents a rich analysis of sexual offences and, in the space remaining, this review will chart three significant themes which emerge.

A first theme is the interaction between sexual autonomy and consent (p. 25) – that is, the need for a liberal regime of sexual offences to protect negative sexual autonomy (i.e. the right not to engage in, or be subjected to, sexual activity to which one does not consent) and not to infringe positive sexual autonomy (i.e. the right to engage in, or be subjected to, sexual activity to which one does consent). In some instances, this sets up an intriguing tension between under- and over-inclusive approaches to criminalising sex, something which Green attempts to reconcile through rational reconstruction. His strategy is to ask: how serious the problem of non-consensual sex is in the first place (in the risk and magnitude of harm); how effective any proposed rule would be at reducing that problem; and how much of a burden the new rule would place on the positive right to engage in genuinely consensual sex – this assessment involving both empirical and normative judgements (p. 89).

Nevertheless, that criminalisation tension is sometimes difficult to handle, not least where non-consent might be presumed (Part II.B). Such a presumption may be too quick in certain cases of incapacity, statutory rape and abuse of position. In these chapters, and by dint of his liberal scheme, Green thereby advocates a more nuanced approach to criminalisation. For example, with regard to mentally disabled people, he suggests a shift from considering the question of capacity to consent, to considering the question of consent “proper” – this entailing a more contextual view of capacity against a backdrop of the actual circumstances in which the sex act occurred (p. 150); and in relation to abuse of position, he recommends criminal sanctions based solely on a public corruption/institutional rationale – limiting criminalisation to police officers, prison guards and probation officers (p. 173). These restrictive strategies find expression elsewhere: for example, he doubts that a liberal criminal law can justify criminalisation of adult incest (pp. 265–72), except in parent/adult child cases where the relationship began when the younger partner was still a child, or, say, if it began when that person was an adult but had been raised by the parent during childhood – and even here there might only be a rebuttable, instead of conclusive, presumption of coercion (p. 276).

A second theme is the contrast in legal regulation of sexual offences across jurisdictions. This is striking in respect of taboo conduct like bestiality (pp. 330–32), but it emerges in connection with rape and sexual assault too. Whilst these crimes have expanded to include not only vaginal penetration (by the penis and, sometimes, other bodily parts or objects), but also anal and oral penetration (thereby envisaging female and male victims), they reveal a discrepancy in labelling. In Canada, along with many Australian and US jurisdictions, the phrase “sexual assault” constitutes an umbrella expression, covering all non-consensual penetration and, sometimes, non-penetrative contact. This practice contrasts with retention in England and Wales of the word “rape” to describe non-consensual (and specifically penile) penetration of the vagina, anus or mouth, with “sexual assault” connoting a lesser infraction aimed at non-consensual sexual touching. Such labelling variations, especially in the arena of sexual offences, are normatively fraught, although Green makes a persuasive argument (at p. 62) that:

In light of these definitional and labelling discussions, Green might have said more about other phenomena: such as so-called “forced-to-penetrate” cases where a female coerces a male into having penile-penetrative intercourse. He briefly references this issue (p. 69), but the assertion that this behaviour now falls within rape (or its sexual-assault equivalent) presupposes male or female perpetrators – something which runs contrary to the view that only males can commit rape, as retained in some countries (not least England and Wales).

A third theme is the distinction between normative and empirical approaches to defining, grading and labelling crimes. These alternative techniques envisage a balance as to whether criminal law should, respectively, shape or reflect public opinion about wrongdoing. Green appears comfortable pursuing the latter technique when considering rape by deceit. Here, in assessing when this should be treated as a crime, he draws a line between those deceptions which undermine consent more harmfully and wrongfully than others. Whilst, normatively, it is contestable as to whether such a line can be drawn – all such deceptions (where they play a “but for” role in inducing consent) could be interpreted as violating negative sexual autonomy – he uses (admittedly now rather old) empirical data, published in 2000, to show that public opinion might endorse a finding of rape by deceit in cases involving: fraudulent medical procedures; spousal or other impersonation; and misrepresentations regarding the offender's sexually transmitted disease (pp. 108–15). There is some ambiguity as to how far Green feels empirical insights should guide offence design: he suggests that criminal law might not always follow community views – for one thing, societal intuitions of justice may not be “correct” (p. 108). But in the pages that follow, and in the absence of a normative claim about criminalising deceptions, he adopts these intuitions for rape by deceit, albeit as a “place to begin analysis” (p. 109). This favourable and yet cautious attitude to empirical lawmaking arises elsewhere in his work – see Thirteen Ways (pp. 56–57) – though it is interesting that he seems to lean towards the former attitude at other junctures in Criminalizing Sex. For example, he cites the maintenance of a consistency between criminal law and social norms as a key commonality in grading and labelling rape (p. 72); whilst under voyeurism and indecent exposure, he stipulates a need to “situate the norms that underlie [this behaviour] in a broader social and cultural context. That is, unless we know what conduct society regards as normal and acceptable, we will hardly be able to say what conduct it views as harmful or wrongful such that criminalization might be an appropriate response” (p. 201).

Overall, Criminalizing Sex is a highly engaging, well written and meticulously researched monograph. It is extremely bold in its legal and jurisdictional coverage and, consequently, offers many useful insights into the changing law on sexual offences throughout the West. Perhaps one of its greatest strengths lies in shedding important criminalisation light on aspects of sexual activity which, hitherto, criminal-law theory has neglected; particularly activity which is taboo. In this regard, Green's ideas about liability in areas like incest, bestiality and necrophilia are enlightening, as indeed they are in alternative spheres like voyeurism and indecent exposure. However, the whole book should be read by anyone with an interest in sexual offences – to that end, it represents another vital special-part contribution by Green.