Free Will, Biological Determinism, and Criminal Justice

| by Tim Rogers |

Is moral responsibility dead?

“We care about free will primarily because we care about what comes along with it – moral responsibility.” — Adina Roskies, 20061

On 20th January 1843 Daniel M’Naghten2, a Scottish woodturner, shot and killed the English civil servant Edward Drummond, who was walking back to Downing Street from Charing Cross. Drummond was the private secretary to the Prime Minister, Robert Peel, who was probably M’Naghten’s intended victim. In any case, M’Naghten was arrested on the spot by a police constable, he appeared before Bow Street magistrate’s court the following morning, and he was tried at the Old Bailey between 2nd and 3rd March 1843 on a charge of “the willful murder of Mr Drummond.”

M’Naghten’s trial is a landmark case within English Law, and in turn it has had a significant impact on other legal jurisdictions around the world, including those of Scotland, Canada, Australia, New Zealand, and the United States. The accused said very little at his trial, but it was clear to all that he was suffering from persecutory delusions. He had already told the Bow Street magistrates that “the Tories in my native city have compelled me to do this. They have entirely destroyed my peace of mind.” When asked to plead at the Old Bailey, all he said was “I was driven to desperation by persecution.”

The only substantial difference between prosecution and defence at the trial was whether he suffered from “partial insanity” or whether his delusional beliefs led to such a breakdown of moral sense and self-control that he was in fact “not guilty on the grounds of insanity.” The medical evidence in this case all pointed to the latter, and, in a remarkable summing up, the judge reminded the jury that if they reached this verdict, the accused would be properly looked after. The jury did not even have to retire; they returned a verdict of not guilty on the grounds of insanity, and M’Naghten was transferred to the State Criminal Lunatic Asylum at Bethlem Hospital south of London.


It is perhaps testament to the rarity of political assassination in the United Kingdom that both prosecution and defense immediately concluded that M’Naghten was insane, but leaving that aside the case is of international importance for a number of reasons. Firstly, the judge’s instructions to the jury included a particular phrasing which allowed the jury to determine whether the purported “defect of reason or disease of the mind” was significant enough to warrant a defense of insanity. Furthermore, the judge made clear that “every man is presumed to be sane” and that therefore the onus was on the defense to prove the existence of severe mental illness. The case was of such high-profile that the House of Lords then asked a panel of experts to consider the matter, and the resulting principles have become established in case-law as the M’Naghten Rules. Whilst not having the authority and status of, say, an Act of Parliament, the Rules or their variants are still relied on in multiple jurisdictions. Indeed, in the USA, many states returned to a M’Naghten interpretation following the attempted shooting of President Reagan in the 1980’s.

One of the surprises in reading about the M’Naghten case is just how humane, compassionate and caring the response of the English Victorian criminal justice system actually was. There had been a long tradition, of course, of treating insane defendants rather differently (and often leniently) but after M’Naghten this was codified and established as case-law. As far as we can tell, this development was accepted without demur by Victorian society at large. The fact that the M’Naghten Rules were later adopted by other English-language nations suggests that this humane response was not a uniquely British thing (although even now, many parts of the world do not treat mentally ill defendants with anything like the compassion of 1843 England).

In M’Naghten the major players seem to have got things just right. The prosecution, defence, judge, jury, the House of Lords and the various experts acted intelligently and with dignity. The broad acceptance of the underlying concepts by wider society (politicians, media, and the general public) must have lent considerable support to the whole process, so that from that time onwards defendants with major mental illness could be given a fair and informed trial.

Fast forward to 2017, however, and we find a legal landscape which is beginning to shift and buckle as a result of hidden pressures. So far, this is a barely perceptible shift. There are arguably two separate developments that will have an impact on how the courts continue to function in this respect, one practical and one philosophical. The practical problem is perhaps the easier to dispose of, as it may be more amenable to new court rules or systems of evidence. The problem is this: the arrival in court of neuroscience in the form of brain scans, EEG’s and “hard data” which become part of a “neurobiological defense.” A paper in the Journal of Law and Biosciences in 20163 examined the growing use of neurological and behavioral genetic evidence by criminal defendants in US courts, and found a steady increase (in fact a trebling of the use of such evidence between 2005 and 2012). Not only that, the time and space devoted to detailed discussion of this evidence within the judges’ opinions also increased.

One leading author in this field, Michael Gazzaniga4, warns that “our understanding of neuroscience will dominate the entire legal system.” Whilst it would be wrong to characterize all of this work as “My brain made me do it,” nevertheless there is a risk of lawyers misusing neuroscience as an all-purpose defense. There is also, as psychiatrist and author Sally Satel5 remarks, “a risk that overzealous neuroscientists exaggerate the capacity of scans to reveal the contents of our minds.” The presence of abnormalities on a brain scan is not the same as the existence of “abnormality of mind” (even normal controls in large studies are frequently found to have various subtle abnormalities). Much of this “neuro-evidence” is at the entirely wrong level of analysis and explanation, because the Court should really be considering concepts such as “competence”, capacity, and consciousness and it is not clear that neuroscientists are able to offer much expertise about these in a forensic setting. Court time is going to be increasingly taken up with detailed consideration of misleading or irrelevant evidence. A combination of bad science and bad science-reporting is likely to lead to loss of trust in the justice system (see, for example, “Brain scans can spot criminals, scientists say”6).

However, this is a relatively trivial problem, which can presumably be overcome by tightening Court procedures and rules of evidence (for example by stricter definitions of what types of evidence are admissible). A second, and inter-related, problem is deeper and less tractable, and takes the discussion away from mere “pathology” to the nature of free will itself. In a nutshell, a bigger problem facing the criminal justice system is how to reconcile the growing consensus within neuroscience that the brain controls all thoughts and actions and that free will is an illusion, with the court’s explicit need to apportion blame or culpability.


This is not a new debate, obviously, but it is one which will become more acute as neuroscience demands to have its day in court. The assertions of a reductionist and deterministic neuroscience (one which is increasingly able to locate the neural drivers of cognition and emotion) and of a high-level behavioral genetics (which attempts to provide heritability estimates for just about every aspect of human behavior) are increasingly incompatible with the age-old notions of free-will and moral responsibility. Most neuroscientists are now, implicitly or explicitly, determinists (although they believe in a complex and subtle determinism).

The challenge this poses to our concepts of jurisprudence and justice is immense. In M’Naghten, remember, the trial judge told the jury that “every man is presumed to be sane,” and didn’t even have to spell out the underlying assumption that every individual is presumed to have free will. This would be a given in Victorian Britain. But is this an assumption that can really be made today? Many scientists and psychologists would now classify free will and moral responsibility as belonging to “folk psychology,” a hangover from a pre-scientific time. It might be thought that such metaphysical speculations are fruitless and have no practical importance, but in the criminal courts they are brought into sharp focus.

There is an argument that folk psychology can contain a deeper truth. Eddy Nahmias and colleagues in Atlanta showed that people’s belief in free will is not challenged by “neuroprediction.”7 In a complex experimental design they found that subjects only felt that free will was threatened if a person’s decisions were manipulated by a neuroscientist, not if decisions were merely predicted via their brain activity. This suggests that our ancient concepts of free will and personal responsibility are untroubled by modern advances in neuroscience. My brain might very well have “made me do it”, but because I am my brain this statement has less significance than some neuroscientists claim.

The American psychologist Carl Rogers, writing in the 1950’s and 1960’s, anticipated some of this debate (while not concerning himself overly with the forensic setting but rather the wider political sphere). Rogers was interested in the behavioral sciences, and in seeing human behavior as part of a deterministic universe, but he was also a staunch defender of human existential freedom (and hence moral responsibility). In a lecture in the 1960’s Rogers gave a trenchant warning against an entirely deterministic view of humanity:

Man has long felt himself to be but a puppet in life – moulded by economic forces, by unconscious forces, by environmental forces…and enslaved by persons, by institutions and by theories of psychological science. But he is firmly setting forth a new declaration of independence. He is discarding the alibis of unfreedom. He is choosing himself, endeavouring in a most difficult and tragic world to become himself – not a puppet, not a slave, not a machine, but his own unique individual self.”8

Rogers was fully aware of the paradox in this. He regarded the experience of “freedom” not as a contradiction to the deterministic universe of cause and effect, but as a complement to such a universe. How this paradox was to be resolved, he was unable to say, for which we can hardly blame him as it is a question which has troubled the wisest minds since the dawn of time.

We move on tracks laid down by the Gods. Or we are puppets dancing on our chromosomes. Or we are simply acting out the inevitable phenomena of our dysfunctional neurochemistry. And in the midst of all this, the courts must continue to do their job, to apportion culpability, and to dispense justice.

We are not good with contradiction.9 We seem to like to tidy up all the loose ends and for everything to make sense. But perhaps this will never happen; we may just have to accept that we are completely determined beings, and we are also free.


Tim Rogers is a Consultant Psychiatrist in Edinburgh. He writes about psychiatry, medicine, diagnostic validity and related themes. Follow him on Twitter @timrogers2016



  1. Roskies A. Neuroscientific challenges to free will and responsibility. Trends in Cognitive Science 2006 sept; 10: 419-423.
  2. The spelling is variously given as M’Naghten, McNaughton, McNaughten etc. in various authorities. The form M’Naghten is used in English and American law reports. See the Wikipedia article on Daniel M’Naghten for a helpful biography
  3. Farahany NA. Neuroscience and behavioural genetics in US criminal law: an empirical analysis. Journal of Law and the Biosciences 2016; 2(3): 485-509.
  4. Gazzaniga M. The Ethical Brain: The science of our moral dilemmas. Harper Perennial, 2006. ISBN-10: 0060884738.
  5. Satel S. Can brain scans explain crime? Interview. Washington Post. 2013 June 10.
  6. Sample I. Brain scans can spot criminals, scientists say. Guardian. 2017 March 13.
  7. Nahmias E, Shepard J, Reuter S. It’s OK if my brain made me do it: people’s intuitions about free will and neuroscientific prediction. Cognition 2014, 133(2): 502-516.
  8. Rogers C. Quoted in Barrett-Lennard G. Carl Rogers’ Helping System; Journey and Substance. Sage, London, 1998. Page 72.
  9. Kaplan E. Can we live with contradiction? New York Times. 2017 Jan 29.
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  1. djaramblings

    The words ‘moral’ and ‘justice’ etc. need to have their meaning’s defined before anything in this discussion can mean anything. In the meantime what society requires is a simple method of ‘ locking up’ (or otherwise treating people ) in order to prevent a minority of individuals behaving in a manner that upsets the majority. Analyzing the state of mind,genetics, etc etc of such people is simply an achademic exercise.

  2. jamzw

    There is a great difference in a strong people allowing for compassion for the few and a weakened people making allowances for the many.

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