First Class Criminal Law Exam with one essays on the M'Naghten Rules and a problem question with regards to offences against the person including GBH, assault and constructive manslaughter. The grades and feedback for each question are at the end of the document.
Although the M’Naghten Rules (MNR) have been relied on as the bedrock of legal standards for assessing
insanity for 180 years, they are significantly outdated and fail to justly distinguish between those who should or
shouldn’t be held criminally liable on the grounds of insanity. The rules are both too broad and too narrow
(Tadros, 2005) and without reform, will continue to proliferate uncertainty and inconsistency with international
standards (ECHR_.
The essay will first provide an overview of the insanity defence and MNR, before critiquing the impact of
applying a legal criterion of responsibility over not a medical understanding of mental illness, and its lack of
consonance with the ECHR. Then, this essay will examine which mental illnesses are included and excluded
from the rules’ ambit, criticising its threshold for determining who is insane, proceeding to highlight judicial
reluctance in Sullivan and critique the judgment of Windle. Finally, this essay will consider reform before
concluding that without Parliamentary action, the insanity defence remains uncertain and unpredictable due to
MNR’s inadequacy as a significantly outdated legal framework.
Insanity defence and MNR
For the defence of insanity to be pleaded, a defendant (D) must prove that they were suffering from a defect of
reason caused by a disease of the mind. The case of M’Naghten (1843) originated the test, establishing this
as meaning that either (i) they did not have knowledge of the nature or quality of their actions, or (ii) they did
not have the knowledge that what they were doing was wrong. Subsequently, D will be found ‘not guilty, but
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, insane’ rendering them fully acquitted (R [2013]) but subject to compulsory detention in a special hospital
(Schedule 1 Criminal Procedure (Insanity and Unfitness to Plead) Act 1991 (CP(IUP)A)). The primary
objective of MNR is to ascertain whether D possessed the requisite mental capacity to form the necessary
mens rea, for a particular offense. Notably, there are debates as to whether a special defence of insanity
should even exist, because if it only functions to negate mens rea then the facts giving rise to insanity could
fall within the scope of other defences such as duress (Morris, 1982). However, this is beyond the scope of
this essay.
However, since these rules were formulated, societal and medical understandings of mental illnesses have
drastically changed and rather act in contention with the outdated MNR, with the term ‘insane’ even being an
offensive or derogatory term. Whilst this may explain the concerned discrepancy between legal and medical
perspectives of mental disorders and why there are very few numbers of successful insanity pleas each year
(Law Commission, 2013), there is no excuse for why this approach hasn’t already been reformed.
A legal vs medical criterion of responsibility
It has been established that for the insanity defence to be pleaded, a ‘disease of the mind’ must be proven
with the burden on D to prove that they did not know the nature and quality of their act or that they did not
understand that it was wrong (M’Naghten). Immediately, this legal criterion places a significant burden of proof
on D to establish a disease of the mind on the balance of probabilities (Sodeman v R [1936]). This makes it
challenging for individuals with mental illnesses to show their lack of understanding or knowledge, increasing
the likelihood of a miscarriage of justice. In recognition of this pitfall, it is challengeable under Article 6(2)
ECHR as contrary to the presumption of innocence (Kebelene [1999]).
Secondly, what constitutes a disease of the mind is deemed to be a solely legal question, despite how a
medical condition should arguably be left to medical experts; the result being the definition is much wider that
justified. The denotation of ‘mind’ is unproblematic with Devlin J in R v Kemp [1957] defining it in the ‘ordinary
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