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Trial by Medicine: a landmark interdisciplinary exploration of legal insanity and criminal responsibility in Victorian Britain

Published online by Cambridge University Press:  27 November 2025

Owen P. O’Sullivan*
Affiliation:
A staff psychiatrist in the Forensic Division of the Complex Care and Recovery Program at the Centre for Addiction and Mental Health, Toronto, and an assistant professor in the Department of Psychiatry, Temerty Faculty of Medicine, University of Toronto, Canada.
Alexander I. F. Simpson
Affiliation:
A staff psychiatrist in the Forensic Division of the Complex Care and Recovery Program at the Centre for Addiction and Mental Health, Toronto, and a professor in the Department of Psychiatry, Temerty Faculty of Medicine, University of Toronto, Canada.
*
Correspondence Owen P. O’Sullivan. Email: owen.osullivan@camh.ca
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Summary

Roger Smith’s Trial by Medicine: Insanity and Responsibility in Victorian Trials traced how Victorian Britain defined legal insanity. Through an interdisciplinary approach, Smith demonstrated how determinations of criminal responsibility were shaped by more than legal reasoning alone, with verdicts also influenced by professional ambition among expert witness groups often with divergent medical opinions, in addition to broader factors such as social class, gender and evolving moral values. Given its rigour and societal insights, it represents a landmark achievement in the field.

Information

Type
Memory Lane
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of Royal College of Psychiatrists

Roger Smith taught in the Department of History at Lancaster University, UK, for 25 years. His interdisciplinary research focused on intersections between law, philosophy and the history of mind and brain. Published in 1981, Trial by Medicine examined the history of legal insanity and criminal responsibility in Victorian Britain (Smith Reference Smith1981).

An era of progress and professionalisation

Advances in the Victorian era encompassed significant changes in how society approached issues such as criminality, poverty and mental illness. Legislative reform, professional policing and the growth of institutions followed. Psychiatry as we know it today started on a pathway towards professionalisation and organisation. Linked to these changes were conceptual tensions between different theories of human behaviour and criminality reflective of a gradual shift towards more humane approaches. High-profile legal insanity cases could engender highly contentious and emotive discussions, and such trials often became a public spectacle. News media aired these conceptual tensions, while courtrooms staged debates on human behaviour, with divergent medical (deterministic) and legal (volitional) paradigms endeavouring to reconcile the seemingly irreconcilable.

Introducing M’Naghten

The case of Daniel M’Naghten in 1843 is a central pillar of criminal jurisprudence (R v M’Naghten (1843)). M’Naghten was a Glaswegian actor-turned-woodcutter known to move in radical political circles. While labouring under conspiratorial persecutory delusions relating to his having voted against a particular Conservative party candidate, he attempted to assassinate the British Prime Minister Sir Robert Peel, but mistakenly killed Peel’s private secretary Edward Drummond.

The case gave rise to the M’Naghten Rules for legal insanity, which have proved hugely influential and enduring. Over the intervening 180 or so years, through precedent or codification, many common law jurisdictions around the world have continued to rely on them to establish legal insanity as an exculpatory defence in criminal law. Beyond the UK, the list includes – among others – Ireland, the USA, Canada, Australia, New Zealand, India and many Caribbean countries. Understanding the origins of any such legal criteria and their associated provisions currently in force will likely trace back to M’Naghten and, more generally, to the prevailing medical, legal, cultural and societal norms and mores of Victorian-era Britain.

Law, psychiatry and the struggle for authority

Smith examined how evolving psychiatric theories and medical rivalries influenced similar cases following M’Naghten. He relied on English and Scottish cases, and considered contemporary coverage in medical journals and periodicals, in addition to asylum medical records. In doing so, he explored the interfaces between – and evolution of – psychiatric expertise, adversarial legal processes and moral views on individual responsibility in the Victorian era and onwards into the 20th century.

A recurring theme related to the degree of instability and contention surrounding legal definitions of mental illness, as evidenced by the extent of divergence and disagreement not only between the medical and legal professions, but also between groups of expert witnesses. These included prison doctors, asylum superintendents and alienists, with the latter arguably representing the forebears of modern forensic psychiatrists. A tension between speculation and a quest for scientific legitimacy frequently characterised expert evidence. Philosophical debates on defining the limits of complex constructs, such as madness, reason, free will, passion and guilt, were central. In time, the factional antagonisms between medical professionals came to reflect broader ideological battles to establish dominance over the assessment of mentally ill offenders before the courts.

The cultural politics of criminal responsibility

Smith appreciated that a deep consideration of the insanity test’s cultural and societal origins was critical to understanding its therapeutic jurisprudential applications. To that end, he explored the influence of class, gender and social mores. A chapter is dedicated to medico-legal views on women, which focused on infanticide and puerperal insanity and considered class-associated factors such as infant neglect and poverty. These analyses illuminate how society viewed gender in this context. Beyond psychosis, Smith also explored prevailing beliefs relating to various other states (e.g. intoxication, alcoholism, sleepwalking and epilepsy) and contentious matters (e.g. intellect, character, heritability, degeneracy and deviancy), which speak to courtroom manifestations of societal anxieties regarding moral order.

Reception

In an era when forensic psychiatry was in its relative infancy, Trial by Medicine was notable for its focus and interdisciplinary methodology. In terms of stature, comparisons were readily made with Nigel Walker’s major works on insanity and the penal system (Walker Reference Walker1965, Reference Walker1968). However, it distinguished itself in its aims to situate the emergence of this legal doctrine within a wider professional, institutional, social and cultural context. Furthermore, it represented a uniquely analytical exploration of the surrounding medico-legal discourses, a distinction made clear in the preface: ‘my primary interest is in what people, notably insanity specialists, thought’ (Smith Reference Smith1981: p. viii). In that sense, Smith’s focus was on the particular language and ideas employed and he considered how these related to patterns of application of medical expertise by the courts.

Two reviews of this work stand out. Michael Ignatieff, the Canadian historian, broadcaster and politician, highlighted how it illustrated the struggles psychiatry experienced in establishing epistemic authority when ‘subjected to merciless inquisition’. He described it as an account of ‘the essentially antagonistic ways, one legal, the other medical, in which we continue to understand the key terms of our moral vocabulary: guilt and responsibility’ (Ignatieff Reference Ignatieff1981). Paul Bowden, a central figure in the development of British forensic psychiatry, wrote that ‘readers will be treated to a work of scholarship that deserves to become a key reference text’ and concluded ‘the courts continue to interpret the law flexibly’, with the acceptance of expert evidence depending on its ‘social utilitarian function and the whims of the judiciary’ (Bowden Reference Bowden1982). In that sense, this book could be argued to have undertaken foundational medico-legal historical and jurisprudential analyses relevant to the emerging specialty.

Epilogue

In 1981, the year of its publication, John Hinckley Jr, a troubled 25-year-old from a wealthy background attempted to assassinate the US President Ronald Reagan by firing six shots outside the Washington Hilton Hotel. He was motivated by a long-standing obsession with the film Taxi Driver and a desire to garner the attention of the actor Jodie Foster owing to an intense infatuation. Hinckley’s acquittal on the grounds of insanity had a seismic impact on the insanity defence in the USA (United States v. Hinckley (1981)). Widespread outrage triggered waves of reform, with the general effect of tightening the provision.

Hinckley re-exposed the tensions between more traditional legal constructs of responsibility and more modern medical understandings of illness. Paul S. Appelbaum in 1994 reflected on Hinckley and the insanity test, and predicted that future cycles of controversy would likely be characterised by conflicting expert evidence in a high-profile case, acquittal and public outcry (Appelbaum Reference Appelbaum1994). This pathway, indeed, seemed all too familiar and unsurprising, having read Smith’s analyses.

Half a century of unfinished reform

In the UK, informed by clinical progress and shaped by political pressures, the latter half of the 20th century witnessed a series of governmental reports and legislative reforms pertaining to mentally disordered offenders. These were focused on patient welfare, institutional transformation and building risk-focused, integrated systems. Among these, the Butler Report was notable in its criticism of the insanity test as essentially outmoded and inadequate (Home Office 1975). Over time, the test has frequently also been criticised for its narrow focus on cognitive understanding as essentially representing too high a bar.

More recently, it has been the subject of a Law Commission review citing these issues (Law Commission 2013). A proposed reform included a broader test reliant on a defendant being deemed not criminally responsible owing to a recognised medical condition, to reflect more contemporary concepts of illness and like provisions in Canada, for example. Notwithstanding the strong recommendations, the Law Commission review was not followed by legislative reform and, as it stands, legal insanity remains anchored to a 19th-century doctrine.

Reflection: conflict by design

For doctors, Trial by Medicine encourages reflection on how psychiatric ethics, standards and aspirations to expert credibility were influenced by societal values and the courts’ needs. Smith argued that M’Naghten did not necessarily cause antagonism between medicine and the law, but rather that its conceptual structure represented an expression of inherent conflicts between the two. In that sense, the cases discussed and analysed serve as clear reminders why legal criteria are not likely by their nature and purpose to map neatly onto medical constructs.

For legal professionals, the work encourages critical analyses on the application of different forms of expert authority. For both, it provokes consideration on the adequacy of methods of determining insanity and invites curiosity as to how medical understanding of mental illness and evolving societal values can shape legal doctrines. Finally, it asks the contemporary reader to consider the power of historical inquiry and the place of medical humanities in educating medical and legal professionals.

Conclusion

Trial by Medicine has made a landmark contribution to the study of expert psychiatric evidence and the evolution of forensic psychiatry more broadly over the past two centuries. Its interdisciplinary approach illustrated how cultural and societal values, contemporary medical practice, legal constructs and the criminal justice system have intersected when the courts have sought – and struggled – to establish criminal responsibility. For trainees, expert witnesses and legal professionals alike, despite the years passed, it continues to offer an avenue to better understand courtroom roles and provides many fascinating insights into the broader contextual origins of relevant legal constructs.

Author contributions

O.P.O’S. prepared the initial draft. A.I.F.S. reviewed and edited the manuscript.

Funding

This research received no specific grant from any funding agency, commercial or not-for-profit sectors.

Declaration of interest

None.

References

References

Appelbaum, PS (1994) Almost a Revolution: Mental Health Law and the Limits of Change. Oxford University Press.10.1093/oso/9780195068801.001.0001CrossRefGoogle Scholar
Bowden, P (1982) Trial by Medicine: Insanity and Responsibility in Victorian Trials (book review). British Journal of Psychiatry, 140: 545.10.1017/S0007125000136700CrossRefGoogle Scholar
Home Office, Department of Health and Social Security (1975) Report of the Committee on Mentally Abnormal Offenders (Cmnd 6244). Her Majesty’s Stationery Office.Google Scholar
Ignatieff, M (1981) Mad or bad? London Review of Books, 3(11). Available from: https://www.lrb.co.uk/the-paper/v03/n11/michael-ignatieff/mad-or-bad.Google Scholar
Law Commission (2013) Criminal Liability: Insanity and Automatism: A Discussion Paper. TSO (The Stationery Office).Google Scholar
Smith, R (1981) Trial by Medicine: Insanity and Responsibility in Victorian Trials. Edinburgh University Press.Google Scholar
Walker, N (1965) Crime and Punishment in Britain. Edinburgh University Press.Google Scholar
Walker, N (1968) Crime and Insanity in England. Edinburgh University Press.Google Scholar

Cases

R v M’Naghten (1843) 8 ER 718.Google Scholar
United States v. Hinckley (1981) 525 F Supp 1342 (DDC).Google Scholar
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