Early Legal Definitions and the “Wild-Beast Test”
Over the last 280 years or so, the law has progressively recognized insanity as an issue and realized that the insane require treatment rather than punishment.
Below, we look at the progress of this evolution and some of the key cases that shaped the law in England up to 1957.
One of the earliest recorded cases of insanity being used as a formal legal defence was Rex v Arnold in 1724.
Edward Arnold was tried at Kingston upon Thames, Surrey, for shooting at Lord Onslow.
In court, Arnold claimed that he had fired upon Onslow because his lordship had bewitched him, sending into his chambers:
“devils and imps that had invaded his bosom such that he could not sleep”.
Arnold’s relatives testified that he suffered from severe, recurring delusions.
The trial judge, Mr. Justice Tracy, instructed the jury that to acquit, they had to decide whether the accused was totally deprived of his understanding and memory and knew what he was doing:
“no more than a wild beast or a brute, or an infant”.
This instruction became known in common law jurisprudence as the “wild-beast test”.
Arnold was convicted and sentenced to death, but was subsequently reprieved at the personal urging of his victim, Lord Onslow.
Although Arnold’s defence failed to secure an outright acquittal, the case established that juries could deliver a “special verdict” of not guilty by reason of insanity, even if the defendant knew what he had physically done (the actus reus or guilty act), provided he lacked the moral understanding that it was wrong and therefore lacked the mens rea (guilty mind) owing to mental disease.
The Case of Earl Ferrers (1760)
The next significant legal development occurred in 1760 at the trial of Lawrence Shirley, the 4th Earl Ferrers.
Ferrers was tried before the House of Lords for the fatal shooting of his estate steward, John Johnson.
At his trial on the 16th of April 1760, Ferrers conducted his own defence and, at his family’s urging, attempted to raise a plea of insanity.
Numerous acquaintances testified to his wild rages, erratic habits, and blatant mental instability.
However, the Solicitor General, Sir Charles Yorke, argued for the Crown that Ferrers had to be found guilty unless the defence could demonstrate that he lacked sufficient mental capacity to comprehend the physical nature and consequences of his actions.
The House of Lords unanimously accepted this strict standard of legal responsibility.
Ferrers was found guilty and subsequently hanged from the scaffold at Tyburn.
James Hadfield and the Criminal Lunatics Act 1800
On the 26th of June 1800, James Hadfield was tried for high treason at the Court of King’s Bench for shooting at King George III at the Theatre Royal in Drury Lane, London, on the 15th of May of that year.
Because it was a trial for treason, the statute permitted Hadfield full representation by defence counsel, represented by the brilliant advocate Thomas Erskine.
The case was heard before Lord Chief Justice Kenyon and two senior judges, prosecuted by both the Attorney General and the Solicitor General.
Thomas Erskine directly challenged the rigid “wild-beast” standard, arguing that an individual could:
“know what he was about”, but be unable to resist his “delusion”.
Erskine arranged for Hadfield to be examined by Dr. John Monro of the Bethlem (Bedlam) Hospital, who confirmed that Hadfield suffered from acute paranoid delusions, almost certainly caused by severe traumatic brain injuries sustained while fighting French troops in 1794.
Erskine explained that Hadfield believed God commanded him continuously, telling him that the world was about to end.
By shooting at the King, Hadfield anticipated that he would be judicially executed and thus achieve death without committing suicide—which was considered both a felony and a mortal sin.
The defence succeeded. Hadfield was acquitted on the grounds of insanity and committed to Bethlem Hospital in Southwark, London.
Hadfield’s trial directly prompted Parliament to pass the Criminal Lunatics Act 1800, which provided:
“in all cases where it shall be given in evidence upon the trial of any person charged with treason, murder, or felony, that such person was insane at the time of the commission of such offence, and such person shall be acquitted, the jury shall be required to find specially whether such person was insane at the time of the commission of such offence, and to declare whether such person was acquitted by them on account of such insanity; and if they shall find that such person was insane at the time of the committing such offence, the court before whom such trial shall be had, shall order such person to be kept in strict custody, in such place and in such manner as to the court shall seem fit, until His Majesty’s pleasure shall be known.”
Prior to this statute, individuals acquitted on the grounds of insanity were frequently discharged back to the care of their relatives, as the criminal courts lacked statutory authority to detain them without separate civil committal proceedings.
Following this, the County Asylums Act 1808 authorized the construction of dedicated institutions for the criminally insane to provide medical care rather than punitive detention. The first county asylum opened in Northampton in 1811, with the number expanding to nine by 1827.
John Bellingham and the Assassination of Spencer Perceval (1812)
Great Britain does not have a long history of political assassinations, but on the 11th of May 1812, just such an event occurred when merchant John Bellingham shot and killed Prime Minister Spencer Perceval in the lobby of the House of Commons.
Bellingham held an obsessive grudge against the British government, blaming the administration for his financial ruin and imprisonment in Russia.
Arrested on the spot, Bellingham was brought to trial four days later at the Old Bailey.
His defence attorney applied for an adjournment to gather witnesses to support an insanity defence, but this request was denied by Lord Chief Justice James Mansfield.
In his summing up to the jury, Lord Mansfield defined partial insanity:
“there is a species of insanity where people take particular fancies into their heads, who are perfectly sane and sound of mind on all other subjects, but this is not a species of insanity which can excuse any person who has committed a crime, unless it so affects his mind at the particular period when he commits the crime as to disable him from distinguishing between good and evil or to judge the consequences of his actions.”
Bellingham was convicted of murder and publicly hanged outside Newgate Prison on the 18th of May 1812, just one week after the assassination.
Daniel M’Naughten and the Landmark Rules of 1843
The landmark case that governed the legal definition of insanity across the English-speaking world for more than a century was that of Daniel M’Naughten.
On the 20th of January 1843, M’Naughten fatally shot Edward Drummond, the private secretary to Prime Minister Sir Robert Peel.
The intended target was Peel himself, but M’Naughten mistook Drummond for the Prime Minister as Drummond left Peel’s residence, shooting him in the back.
M’Naughten was arrested immediately. He suffered from intense persecutory delusions, believing that Peel and the Conservative Party were orchestrating a conspiracy to ruin his life.
At his trial at the Old Bailey on the 27th of February 1843 before Lord Chief Justice Tindal, medical experts who treated “lunatics” testified that M’Naughten suffered from monomania, stating that his delusions deprived him of self-control.
Lord Chief Justice Tindal directed the jury:
“the question to be determined is, whether at the time the act in question was committed, the prisoner had or had not the use of his understanding, so as to know that he was doing a wrong or wicked act.”
The jury returned a verdict of not guilty on grounds of insanity, and M’Naughten was committed to Bethlem Hospital.
The acquittal of a political assassin sparked public controversy, prompting Queen Victoria and the House of Lords, led by Lord Chancellor Lyndhurst, to formulate standard legal guidelines.
The Law Lords issued the famous M’Naughten Rules, establishing:
“To establish a defence on the ground of insanity, it must clearly be proved that, at the time of the committing of the act, the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or if he did know it, that he did not know he was doing was wrong.”
Victorian Reforms, Broadmoor, and the 1884 Act
The Lunacy Act 1845 created the Lunacy Commission, chaired for forty years by the 7th Earl of Shaftesbury (Anthony Ashley-Cooper), transforming mentally ill offenders from “prisoners” into “patients.”
Asylums were regulated under the County Asylums Act 1845, allowing patients to be discharged if certified recovered by medical superintendents.
On the 25th of August 1883, Parliament enacted the Trial of Lunatics Act 1883.
At the personal request of Queen Victoria—who had herself survived eight assaults by mentally disturbed individuals—the special verdict was formally altered from “not guilty on the ground of insanity” to “guilty but insane.”
The Criminal Lunatics Act 1884 introduced significant safeguards.
Section 2 empowered the Home Secretary to order an independent medical examination by two qualified doctors whenever there was reason to believe that a prisoner under sentence of death was insane.
If confirmed, the prisoner was reprieved and transferred to Broadmoor Criminal Lunatic Asylum, which had opened in 1863.
Individuals committed under executive order were designated as “Secretary of State’s lunatics.”
In 1884/85 alone, 938 criminal lunatics were identified, with 163 committed to asylums by the Home Secretary prior to standing trial.
Mid-20th-Century Inquiries and Criminal Responsibility
In 1923, the Committee on Insanity and Crime, chaired by Lord Justice Atkin, issued its report on the 1st of November.
The Atkin Committee recommended that the law recognize an “irresistible impulse” defence where a mental disease substantially deprived the accused of the power to resist their actions.
The committee highlighted instances of maternal infanticide, where young mothers, overwhelmed by mental illness, killed their newborns knowing it was legally wrong, but driven by an uncontrollable impulse (a dilemma seen in earlier trials like Mary Morgan in 1805 and Sarah Jones in 1827).
The committee also recommended that unfitness to plead should require testimony from at least two medical practitioners, and that the Home Office establish formal provisions for psychiatric examinations.
However, subsequent inquiries—including the 1930 Select Committee on Capital Punishment and the 1953 Royal Commission on Capital Punishment chaired by Sir Ernest Gowers—saw their recommendations regarding irresistible impulse rejected by senior judges, who cautioned that partial insanity defences would undermine individual criminal accountability.
The Four Stages of Insanity Assessment (1900–1949)
By 1947, English law provided four distinct procedural stages at which the sanity of a person charged with murder could be evaluated:
- Prior to Trial: The accused could be certified insane and transferred to Broadmoor under Section 2 of the Criminal Lunatics Act 1884.
- On Arraignment: A jury could find the accused unfit to plead under Section 2 of the Criminal Lunatics Act 1800 (occurring in 49 cases between 1900 and 1949).
- At Trial: A jury could return a verdict of “guilty but insane” under the Trial of Lunatics Act 1883, leading to indefinite detention at Her Majesty’s Pleasure (428 out of 3,130 defendants tried for murder between 1900 and 1949 were found insane).
- Post-Sentence Statutory Inquiry: If a condemned prisoner appeared insane while awaiting execution, Section 2 of the Criminal Lunatics Act 1884 required the Home Secretary to appoint two or more doctors to inquire into their sanity. If certified insane, the death sentence was automatically respited, and the prisoner was transferred to Broadmoor.
Between 1900 and 1949, 1,080 men and 130 women were convicted of murder in England and Wales.
Statutory medical inquiries were convened in the cases of 186 men and 6 women (16% of all capital convictions).
These inquiries resulted in:
- 46 men and 2 women being certified insane;
- 36 men and 1 woman reprieved on the grounds of mental instability;
- 94 men and 2 women executed after the medical inquiry confirmed their sanity.
Because death was the mandatory sentence for murder prior to 1957, insanity was often raised as the sole legal recourse to avoid execution.
Extraordinary Cases: John Thomas Straffen and Ruth Ellis
One of the most extraordinary murder cases involving severe mental illness was that of John Thomas Straffen.
Straffen had spent years in institutions and was committed to Broadmoor in October 1951 after strangling two young girls in Bath (Brenda Goddard and Cicely Batstone), having been found unfit to plead by reason of insanity.
On the 29th of April 1952, Straffen escaped from Broadmoor and strangled five-year-old Linda Bowyer before being recaptured twenty hours later.
Put on trial for this third murder at Winchester Assizes, the jury found him fit to plead, rejected his insanity plea, and convicted him of murder.
Sentenced to death, Straffen was subsequently reprieved on grounds of mental defect by Home Secretary Sir David Maxwell Fyfe.
Straffen spent the rest of his life in prison, dying at Frankland Prison in County Durham on the 19th of November 2007 at the age of 77—Britain’s longest-serving prisoner.
Conversely, the case of Ruth Ellis in 1955 illustrated the strict boundaries of legal sanity under the M’Naughten Rules.
Following the shooting of her lover David Blakely, Ellis was held in Holloway Prison’s hospital wing under continuous medical observation.
Dr. M. R. Penry Williams, the Principal Medical Officer, examined her twice and found no psychosis.
On the 3rd of May 1955, an electroencephalogram (EEG) revealed normal brain wave function.
Further psychiatric examinations conducted by Dr. D. Whittaker for the defence and Dr. A. Dalzell for the Home Office found no delusions, hallucinations, or disease of the mind.
Under the M’Naughten Rules, Ellis was held legally responsible and hanged on the 13th of July 1955.
The Homicide Act 1957 and Diminished Responsibility
The limitations of the M’Naughten Rules led to statutory reform under Section 2(1) of the Homicide Act 1957, which introduced the Scottish legal doctrine of diminished responsibility into English law:
“Where a person kills, or is party to the killing of another, he shall not be convicted of murder but shall be convicted of manslaughter, if he was suffering from such abnormality of mind (whether arising from a condition of arrested or retarded development of mind or any inherent causes or induced by disease or injury) as substantially impaired his mental responsibility for his acts and omissions in doing or being a party to the killing.”
A successful plea of diminished responsibility reduced the charge from capital murder to manslaughter, granting judges discretionary sentencing options ranging from life imprisonment and hospital orders to probation.
In 2000, the House of Lords expanded the common law defence of provocation, acknowledging that individuals trapped in abusive relationships could experience a loss of self-control driven by fear and despair rather than sudden rage.
This became known as the “battered woman” defence, removing the historical requirement that provocation occur immediately prior to the killing and recognizing why victims might strike while their abusers were asleep.
English law maintains a distinction between legal insanity (a profound disease of the mind eliminating rational understanding) and personality abnormalities, ensuring that those who retain cognitive control remain legally answerable for their crimes.
Frequently Asked Questions
What were the M’Naughten Rules of 1843?
The M’Naughten Rules established the common law standard for the insanity defence. To be acquitted on grounds of insanity, the defence must prove that at the time of the offence, the accused had such a defect of reason from a disease of the mind that they did not understand the nature and quality of their act, or did not know that what they were doing was wrong.
What was the “wild-beast test” in early English law?
Originating in the 1724 trial of Edward Arnold for shooting Lord Onslow, the “wild-beast test” instructed juries that an individual could be acquitted for insanity only if they were totally deprived of reason and memory, knowing what they were doing no more than an infant or a wild brute.
What did the Criminal Lunatics Act 1800 change?
Passed following the trial of James Hadfield for shooting at King George III, the 1800 Act required juries to return a “special verdict” of not guilty by reason of insanity, granting courts the power to detain mentally ill defendants indefinitely in secure custody at the Crown’s pleasure rather than releasing them.
What was the difference between “guilty but insane” and “not guilty by reason of insanity”?
Under the Trial of Lunatics Act 1883, passed at the insistence of Queen Victoria, the verdict was changed from an acquittal (“not guilty by reason of insanity”) to “guilty but insane.” This ensured that mentally disordered offenders were formally labeled as having committed the criminal act before being remanded indefinitely to Broadmoor.
How did the Homicide Act 1957 reform the law on mental illness?
Section 2 of the Homicide Act 1957 introduced the defence of diminished responsibility. It allowed defendants suffering from an abnormality of the mind that substantially impaired their mental responsibility to be convicted of manslaughter rather than capital murder, protecting them from the mandatory death sentence.
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