The insanity defense, also known as the mental disorder defense, is an affirmative
defense
Defense or defence may refer to:
Tactical, martial, and political acts or groups
* Defense (military)
A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is ty ...
by
excuse
In jurisprudence
Jurisprudence, or legal theory, is the theoretical study of the propriety of law
Law is a system
A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to for ...

in a
criminal case
Criminal law is the body of law
Law is a system
A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole.
A system, surrounded and influenced by its env ...
, arguing that the defendant is not responsible for their actions due to an episodic or persistent
psychiatric disease at the time of the criminal act. This is contrasted with an excuse of
provocation
Provocation, provoke or provoked may refer to:
* Provocation (legal), a type of legal defense in court which claims the "victim" provoked the accused's actions
* Agent provocateur, a (generally political) group that tries to goad a desired resp ...
, in which the defendant is responsible, but the responsibility is lessened due to a temporary mental state.
[''Criminal Law - Cases and Materials'', 7th ed. 2012, ]Wolters Kluwer Law & Business
Wolters Kluwer N.V. () is an American Dutch information services company. The company is headquartered in Alphen aan den Rijn, Netherlands (Global) and Philadelphia, United States (corporate). Wolters Kluwer in its current form was founded in 198 ...
; John Kaplan, Robert Weisberg
Robert I. Weisberg is an American lawyer. He is an Edwin E. Huddleson, Jr. Professor of Law at Stanford Law School, and an expert on criminal law and criminal procedure, as well as a leading scholar in the law and literature movement.
Weisberg was ...

, Guyora Binder, , It is also contrasted with a finding that a defendant cannot stand trial in a criminal case because a mental disease prevents them from effectively assisting counsel, from a
civil
Civil may refer to:
*Civic virtue, or civility
*Civil action, or lawsuit
*Civil affairs
*Civil and political rights
*Civil disobedience
*Civil engineering
*Civil (journalism), a platform for independent journalism
*Civilian, someone not a member ...
finding in
trusts
A trust is a legal relationship in which the holder of a right (eg. title to a chattel) gives it to another person or entity who must keep and use it solely for another's benefit. In English common law
English law is the common law legal sy ...
and
estate
Estate or The Estate may refer to:
Law
* Estate (law), a term in common law for a person's property, entitlements and obligations
* Estates of the realm, a broad social category in the histories of certain countries.
** The Estates, representative ...
s where a will is nullified because it was made when a mental disorder prevented a
testator
A testator () is a person
A person (plural people or persons) is a being that has certain capacities or attributes such as reason
Reason is the capacity of consciously applying logic
Logic is an interdisciplinary field which studies trut ...
from recognizing the natural objects of their bounty, and from involuntary
civil commitment
Involuntary commitment, civil commitment, or involuntary hospitalization (also known informally as sectioning or being sectioned in some jurisdictions, such as the United Kingdom
The United Kingdom of Great Britain and Northern Ireland, co ...
to a mental institution, when anyone is found to be
gravely disabled or to be a danger to themselves or to others.
[
Exemption from full criminal punishment on such grounds dates back to at least the ]Code of Hammurabi
The Code of Hammurabi is a Babylonian legal text composed 1755–1750 BC. It is the longest, best-organised, and best-preserved legal text from the ancient Near East. It is written in the Old Babylonian dialect of Akkadian, purportedly by Ham ...

. Legal definitions of insanity or mental disorder are varied, and include the M'Naghten Rule
The M'Naghten rule (pronounced, and sometimes spelled, McNaughton) is any variant of the 1840s jury instruction in a criminal case when there is a Insanity defense, defence of insanity:
The rule was formulated as a reaction to the acquittal in ...
, the Durham rule, the , the ALI ruleThe ALI rule, or American Law Institute Model Penal Code rule, is a recommended rule for instructing juries how to find a defendant
A defendant is a person
A person (plural people or persons) is a being that has certain capacities or attributes ...
(American Legal Institute Model Penal Code rule), and other provisions, often relating to a lack of ''mens rea
''Mens rea'' (; Law Latin Law Latin, sometimes written L.L. or L. Lat., and sometimes derisively called Dog Latin
Dog Latin, also known as Cod Latin, macaronic Latin, mock Latin, or Canis Latinicus, refers to the creation of a phrase
In every ...
'' ("guilty mind"). In the criminal law
Criminal law is the body of law
Law is a system
A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole.
A system, surrounded and influenced by its env ...
s of Australia and Canada, statutory legislation enshrines the ''M'Naghten Rules'', with the terms defense of mental disorder, defense of mental illness or not criminally responsible by reason of mental disorder employed. Being incapable of distinguishing right from wrong is one basis for being found to be legally insane as a criminal defense
In the field of criminal law
Criminal law is the body of law
Law is a system
A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole.
A system, surrounded ...
. It originated in the ''M'Naghten Rule'', and has been reinterpreted and modernized through more recent cases, such as '' People v. Serravo''.[
In the United Kingdom, Ireland, and the United States, use of the defense is rare.] Mitigating factors, including things not eligible for the insanity defense such as intoxication (or, more frequently, diminished capacity
''Diminished Capacity'' is a 2008 comedy film directed by Terry Kinney
Terry Kinney (born January 29, 1954) is an American actor and theatre director, and is a founding member of the Steppenwolf Theatre Company, with John Malkovich, Laurie Me ...
), may lead to reduced charges or reduced sentences.
The defense is based on evaluations by forensic mental health professionals with the appropriate test according to the jurisdiction. Their testimony guides the jury, but they are not allowed to testify to the accused's criminal responsibility, as this is a matter for the jury to decide. Similarly, mental health practitioners are restrained from making a judgment on the "ultimate issue"—whether the defendant is insane.
Some jurisdictions require the evaluation to address the defendant's ability to control their behavior at the time of the offense (the volitional limb). A defendant claiming the defense is pleading "not guilty by reason of insanity" (NGRI) or "guilty but insane or mentally ill" in some jurisdictions which, if successful, may result in the defendant being committed to a psychiatric facility for an indeterminate period.
Non compos mentis
''Non compos mentis
''Non compos mentis'' is a List of legal Latin terms, Latin legal phrase that translates to "of unsound mind": ''nōn'' ("not") prefaces ''compos mentis'', meaning "having control of one's mind". This phrase was first used in thirteenth-century En ...
'' (Latin) is a legal term meaning "not of sound mind". ''Non compos mentis'' derives from the Latin
Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became ...

''non'' meaning "not", ''compos'' meaning "having command" or "composed", and ''mentis'' (genitive
In grammar
In linguistics
Linguistics is the scientific study of language, meaning that it is a comprehensive, systematic, objective, and precise study of language. Linguistics encompasses the analysis of every aspect of language, a ...
singular
Singular may refer to:
* Singular, the grammatical number
In linguistics, grammatical number is a grammatical category of nouns, pronouns, adjectives, and verb agreement (linguistics), agreement that expresses count distinctions (such as "one", ...
of ''mens
In , Mens, also known as Mens Bona ( for "Good Mind"), was the of thought, consciousness and the mind, and also of "right-thinking". Her festival was celebrated on June 8. A temple on the in Rome was vowed to Mens in 217 BC on advice from the , a ...
''), meaning "of mind". It is the direct opposite of ''Compos mentis
A number of Latin
Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Rep ...
'' (of a sound mind).
Although typically used in law, this term can also be used metaphorically or figuratively; e.g. when one is in a confused state, intoxicated, or not of sound mind. The term may be applied when a determination of competency needs to be made by a physician for purposes of obtaining informed consent
Informed consent is a principle in medical ethics
Medical ethics is an applied branch of ethics
Ethics or moral philosophy is a branch of philosophy
Philosophy (from , ) is the study of general and fundamental questions, such as those a ...
for treatments and, if necessary, assigning a surrogate to make health care decisions. While the proper sphere for this determination is in a court of law, this is practically, and most frequently, made by physicians in the clinical setting.
In English law, the rule of ''non compos mentis'' was most commonly used when the defendant invoked religious or magical explanations for behaviour.
History
The concept of defense by insanity has existed since ancient Greece
Ancient Greece ( el, Ἑλλάς, Hellás) was a civilization belonging to a period of History of Greece, Greek history from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, antiquity ( AD 600). This era wa ...
and Rome
, established_title = Founded
, established_date = 753 BC
, founder = King Romulus
, image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Lazio, Italy).svg
, map_caption = The te ...

. However, in colonial America
The colonial history of the United States covers the history of European colonization of North America from the early 17th century until the incorporation of the Thirteen Colonies into the United States of America, after the American Revolu ...
a delusion
A delusion is a false fixed belief that is not amenable to change in light of conflicting evidence. As a pathology, it is distinct from a belief based on false or incomplete information, confabulation, dogma, illusion, hallucination, or some ot ...

al Dorothy Talbye was hanged
Hanging is the suspension of a person by a noose
A noose is a loop at the end of a rope
A rope is a group of yarn
Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, croc ...

in 1638 for murdering her daughter, as at the time Massachusetts
Massachusetts (, ), officially the Commonwealth of Massachusetts, is the most populous state
State may refer to:
Arts, entertainment, and media Literature
* ''State Magazine'', a monthly magazine published by the U.S. Department of State
* ...

's common law
In law, common law (also known as judicial precedent or judge-made law, or case law
Case law is the collection of past legal decisions written by courts and similar tribunal
A tribunal, generally, is any person or institution with authority ...
made no distinction between insanity
Insanity, madness, and craziness are terms that describe a spectrum
A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum
Continuum ma ...

(or mental illness
A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such features may be persistent, relapsing
In internal medici ...
) and criminal behavior. Edward II
Edward II (25 April 1284 – 21 September 1327), also called Edward of Caernarfon, was King of England
This list of kings and queens of the begins with , who initially ruled , one of the which later made up modern England. A ...

, under English Common law, declared that a person was insane if their mental capacity was no more than that of a "wild beast" (in the sense of a dumb animal, rather than being frenzied). The first complete transcript of an insanity trial dates to 1724. It is likely that the insane, like those under 14, were spared trial by ordeal
Trial by ordeal was an ancient judicial practice by which the guilt or innocence of the accused was determined by subjecting them to a painful, or at least an unpleasant, usually dangerous experience.
In medieval
In the history of Euro ...
. When trial by jury replaced this, the jury members were expected to find the insane guilty but then refer the case to the King for a Royal Pardon. From 1500 onwards, juries could acquit the insane, and detention required a separate civil procedure.[, pp15–16.] The Criminal Lunatics Act 1800, passed with retrospective effect following the acquittal of James Hadfield
James Hadfield or Hatfield (1771/1772 – 23 January 1841) attempted to assassinate George III of the United Kingdom
George III (George William Frederick; 4 June 173829 January 1820) was King of Great Britain and Ireland
Ireland (; ...
, mandated detention at the regent's pleasure (indefinitely) even for those who, although insane at the time of the offence, were now sane.
The M'Naghten Rules
The M'Naghten rule (pronounced, and sometimes spelled, McNaughton) is any variant of the 1840s jury instruction in a criminal case when there is a defence of insanity:
The rule was formulated as a reaction to the acquittal in 1843 of Daniel ...
of 1843 were not a codification or definition of insanity but rather the responses of a panel of judges to hypothetical questions posed by Parliament in the wake of Daniel M'Naghten
Daniel M'Naghten (sometimes spelled McNaughtan or McNaughton) (1813–3 May 1865) was a Scottish woodturner who assassinated English civil servant Edward Drummond while suffering from paranoid delusion
A delusion is a fixed belief that is ...
's acquittal for the homicide of Edward Drummond, whom he mistook for British
British may refer to:
Peoples, culture, and language
* British people
The British people, or Britons, are the citizens of the United Kingdom of Great Britain and Northern Ireland
The United Kingdom of Great Britain and Northern Ir ...

Prime Minister
A prime minister or a premier is the head of the cabinet
Cabinet or The Cabinet may refer to:
Furniture
* Cabinetry, a box-shaped piece of furniture with doors and/or drawers
* Display cabinet, a piece of furniture with one or more transpa ...
Robert Peel
Sir Robert Peel, 2nd Baronet, (5 February 1788 – 2 July 1850) was a British Conservative Party (UK), Conservative statesman who served twice as Prime Minister of the United Kingdom (1834–1835 and 1841–1846) simultaneously serving as Cha ...

. The rules define the defense as "at the time of committing 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 as not to know that what he was doing was wrong."[.] The key is that the defendant could not appreciate the nature of his actions during the commission of the crime.
In '' Ford v. Wainwright'' 477 U.S. 399 (1986), the US Supreme Court
The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States of America
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or Americ ...

upheld the common law
In law, common law (also known as judicial precedent or judge-made law, or case law
Case law is the collection of past legal decisions written by courts and similar tribunal
A tribunal, generally, is any person or institution with authority ...
rule that the insane cannot be executed
Capital punishment, also known as the death penalty, is the State (polity), state-sanctioned killing of a person as punishment for a crime. The sentence (law), sentence ordering that someone is punished with the death penalty is called a dea ...
. It further stated that a person under the death penalty is entitled to a competency evaluation and to an evidentiary hearing in court on the question of his competency to be executed.
In '' Wainwright v. Greenfield'', the Court ruled that it was fundamentally unfair for the prosecutor
A prosecutor is a legal representative of the prosecution in states with either the common law
In law, common law (also known as judicial precedent or judge-made law, or case law
Case law is the collection of past legal decisions written by co ...
to comment during the court proceedings on the petitioner's silence invoked as a result of a Miranda warning#REDIRECT Miranda warning
In the United States
The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a country Contiguous United States, primarily located in North America. It consists of 5 ...
. The prosecutor had argued that the respondent's silence after receiving Miranda warnings was evidence of his sanity.
Application
Incompetency and mental illness
An important distinction to be made is the difference between competency and criminal responsibility.
*The issue of competency is whether a defendant is able to adequately assist his attorney in preparing a defense, make informed decisions about trial strategy and whether to plead guilty, accept a plea agreement or plead not guilty. This issue is dealt with in law as "fitness to pleadIn the law of England and Wales, fitness to plead is the capacity of a defendant in criminal proceedings to comprehend the course of those proceedings. The concept of fitness to plead also applies in Scots law, Scots and Law of the Republic of Irelan ...
".
Competency largely deals with the defendant's present condition, while criminal responsibility addresses the condition at the time the crime was committed.
In the United States, a trial in which the insanity defense is invoked typically involves the testimony of psychiatrist
A psychiatrist is a physician
A physician (American English), medical practitioner (English in the Commonwealth of Nations, Commonwealth English), medical doctor, or simply doctor, is a professional who practices medicine, which is c ...
s or psychologist
A psychologist is a professional who practices psychology and studies normal and abnormal mental states, perceptual, cognitive, emotional, and social processes and behavior by experimenting with, and observing, interpreting, and recording how ...
s who will, as expert witness
An expert witness, particularly in common law
In law, common law (also known as judicial precedent or judge-made law, or case law) is the body of law created by judges and similar quasi-judicial tribunals by virtue of being stated in written ...
es, present opinions on the defendant's state of mind at the time of the offense.
Therefore, a person whose mental disorder is not in dispute is determined to be sane if the court decides that despite a "mental illness" the defendant was responsible for the acts committed and will be treated in court as a normal defendant. If the person has a mental illness and it is determined that the mental illness interfered with the person's ability to determine right from wrong (and other associated criteria a jurisdiction may have) and if the person is willing to plead guilty or is proven guilty in a court of law, some jurisdictions have an alternative option known as either a Guilty but Mentally Ill (GBMI) or a Guilty but Insane verdict. The GBMI verdict is available as an alternative to, rather than in lieu of, a "not guilty by reason of insanity" verdict. Michigan
Michigan () is a state
State may refer to:
Arts, entertainment, and media Literature
* ''State Magazine'', a monthly magazine published by the U.S. Department of State
* The State (newspaper), ''The State'' (newspaper), a daily newspaper ...

(1975) was the first state to create a GBMI verdict, after two prisoners released after being found NGRI committed violent crimes within a year of release, one raping two women and the other killing his wife.
Temporary insanity
The notion of temporary insanity argues that a defendant ''was'' insane during the commission of a crime, but they later regained their sanity after the criminal act was carried out. This legal defense is commonly used to defend individuals that have committed crimes of passion
A crime of passion (French: ''crime passionnel''), in popular usage, refers to a violent crime, especially homicide, in which the perpetrator commits the act against someone because of sudden strong impulse such as sudden rage rather than as a ...
. The defense was first successfully used by U.S. Congressman Daniel Sickles
Daniel Edgar Sickles (October 20, 1819May 3, 1914) was an American politician, soldier, and diplomat.
Born to a wealthy family in New York City
New York City (NYC), often simply called New York, is the List of United States cities by popula ...

of New York
New York most commonly refers to:
* New York City, the most populous city in the United States, located in the state of New York
* New York (state), a state in the northeastern United States
New York may also refer to:
Film and television
* New ...
in 1859 after he had killed his wife's lover, Philip Barton Key
Philip Barton Key (April 12, 1757 – July 28, 1815), was an American Loyalist
Loyalism, in the United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is ...
.
Mitigating factors and diminished capacity
The United States Supreme Court
The Supreme Court of the United States (SCOTUS) is the highest court in the Federal judiciary of the United States, federal judiciary of the United States of America. It has ultimate and largely Procedures of the Supreme Court of the United ...

(in '' Penry v. Lynaugh'') and the United States Court of Appeals for the Fifth Circuit
The United States Court of Appeals for the Fifth Circuit (in case citations, 5th Cir.) is a United States federal court, federal court with appellate jurisdiction over the United States district court, district courts in the following United Stat ...
(in ''Bigby v. Dretke
''Bigby v. Dretke'' 402 F.3d 551 (5th Cir. 2005), the U.S. Court of Appeals for the Fifth Circuit heard a case appealed from the United States District Court for the Northern District of Texas
The United States District Court for the Northern Dis ...
'') have been clear in their decisions that jury instructions
Jury instructions, directions to the jury, or judge's charge are legal law, rules that jurors should follow when deciding a case. They are a type of jury control procedures, jury control procedure to support a fair trial.
Description
Jury inst ...
in death penalty cases that do not ask about mitigating factor
In criminal law
Criminal law is the body of law
Law is a system
A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole.
A system, surrounded and inf ...
s regarding the defendant's mental health
Mental health is "a state of well-being
Well-being, also known as ''wellness'', ''prudential value'' or ''quality of life'', refers to what is intrinsically valuable relative ''to'' someone. So the well-being of a person is what is ultimatel ...

violate the defendant's Eighth Amendment rights, saying that the jury is to be instructed to consider mitigating factors when answering unrelated questions. This ruling suggests specific explanations to the jury are necessary to weigh mitigating factors.
Diminished responsibility or diminished capacity can be employed as a mitigating factor or partial defense to crimes. In the United States, diminished capacity is applicable to more circumstances than the insanity defense. The Homicide Act 1957 is the statutory basis for the defense of diminished responsibility in England and Wales, whereas in Scotland it is a product of case law. The number of findings of diminished responsibility has been matched by a fall in unfitness to plead and insanity findings. A plea of diminished capacity is different from a plea of insanity in that "reason of insanity" is a full defense while "diminished capacity" is merely a plea to a lesser crime.
Withdrawal or refusal of defense
Several cases have ruled that persons found not guilty by reason of insanity may not withdraw the defense in a habeas
(; from Medieval Latin
Medieval Latin was the form of Latin
Latin (, or , ) is a classical language
A classical language is a language
A language is a structured system of communication
Communication (from Latin '' ...
petition to pursue an alternative, although there have been exceptions in other rulings. In Colorado v. Connelly, 700 A.2d 694 (Conn. App. Ct. 1997), the petitioner who had originally been found not guilty by reason of insanity and committed for ten years to the jurisdiction of a Psychiatric Security Review Board, filed a pro se
''Pro se'' legal representation ( or ) comes from Latin ''pro se'', meaning "for oneself" or "on behalf of themselves", which in modern law means to argue on one's own behalf in a legal proceedingLegal proceeding is an activity that seeks to in ...
writ of ''habeas corpus
(; from Medieval Latin
Medieval Latin was the form of Latin
Latin (, or , ) is a classical language
A classical language is a language
A language is a structured system of communication
Communication (from Latin '' ...
'' and the court vacated his insanity acquittal. He was granted a new trial and found guilty of the original charges, receiving a prison sentence of 40 years.
In the landmark case
Landmark court decisions, in present-day common law
In law, common law (also known as judicial precedent or judge-made law, or ) is the body of law created by judges and similar quasi-judicial by virtue of being stated in written opinions. ' is ...
of '' Frendak v. United States'' in 1979, the court ruled that the insanity defense cannot be imposed upon an unwilling defendant if an intelligent defendant voluntarily wishes to forgo the defense.
Usage
This increased coverage gives the impression that the defense is widely used, but this is not the case. According to an eight-state study, the insanity defense is used in less than 1% of all court cases and, when used, has only a 26% success rate. Of those cases that were successful, 90% of the defendants had been previously diagnosed with mental illness.
Psychiatric treatment
Those found to have been not guilty by reason of mental disorder or insanity are generally then required to undergo psychiatric
Psychiatry is the specialty (medicine), medical specialty devoted to the diagnosis, prevention, and treatment of mental disorders. These include various maladaptations related to mood, behaviour, cognition, and perceptions. See glossary of psyc ...
treatment in a mental institution, except in the case of temporary insanity (see below
See or SEE may refer to:
Arts, entertainment, and media
* Music:
** See (album), ''See'' (album), studio album by rock band The Rascals
*** "See", song by The Rascals, on the album ''See''
** See (Tycho song), "See" (Tycho song), song by Tycho
* T ...
). In England and Wales, under the Criminal Procedure (Insanity and Unfitness to Plead) Act of 1991 (amended by the Domestic Violence, Crime and Victims Act, 2004 to remove the option of a guardianship order), the court can mandate a hospital order, a restriction order (where release from hospital requires the permission of the Home Secretary), a "supervision and treatment" order, or an absolute discharge. Unlike defendants who are found guilty of a crime, they are not institutionalized for a fixed period, but rather held in the institution until they are determined not to be a threat. Authorities making this decision tend to be cautious, and as a result, defendants can often be institutionalized for longer than they would have been incarcerated in prison.
Worldwide
Australia
In Australia there are nine law units, each of which may have different rules governing mental impairment defenses.
South Australia
In South Australia
South Australia (abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Austral ...

, the Criminal Law Consolidation Act 1935 (SA) provides that:
269C—Mental competence
A person is mentally incompetent to commit an offence if, at the time of the conduct alleged to give rise to the offence, the person is suffering from a mental impairment and, in consequence of the mental impairment—
:(a) does not know the nature and quality of the conduct; or
:(b) does not know that the conduct is wrong; or
:(c) is unable to control the conduct.
269H—Mental unfitness to stand trial
A person is mentally unfit to stand trial on a charge of an offence if the person's mental processes are so disordered or impaired that the person is—
:(a) unable to understand, or to respond rationally to, the charge or the allegations on which the charge is based; or
:(b) unable to exercise (or to give rational instructions about the exercise of) procedural rights (such as, for example, the right to challenge jurors); or
:(c) unable to understand the nature of the proceedings, or to follow the evidence or the course of the proceedings.
Victoria
In Victoria
Victoria most commonly refers to:
* Victoria (Australia), a state of the Commonwealth of Australia
* Victoria, British Columbia, provincial capital of British Columbia, Canada
* Victoria (mythology), Roman goddess of Victory
* Victoria, Seychelles ...
the current defence of mental impairment was introduced in the ''Crimes (Mental Impairment and Unfitness to be Tried) Act'' 1997 which replaced the common law defence of insanity and indefinite detention at the governor's pleasure with the following:
:the accused was suffering from a mental impairment; and
:the mental impairment affected the accused so they either did not understand the nature and quality of the conduct, or did not know that it was wrong.
These requirements are almost identical to the M'Naghten Rules, substituting "mental impairment" for "disease of the mind".
New South Wales
In New South Wales, the defence has been renamed the 'Defence of Mental Illness' in Part 4 of the ''Mental Health (Forensic Provisions) Act 1990''. However, definitions of the defence are derived from M'Naghten's case and have not been codified. Whether a particular condition amounts to a disease of the mind is not a medical but a legal question to be decided in accordance with the ordinary rules of interpretation. This defence is an exception to the ''Woolmington v DPP'' (1935) 'golden thread', as the party raising the issue of the defence of mental illness bears the burden of proving this defence on the balance of probabilities.[.] Generally, the defence will raise the issue of insanity. However, the prosecution can raise it in exceptional circumstances: ''R v Ayoub (1984).''
Australian cases have further qualified and explained the ''M'Naghten Rules''. The NSW Supreme Court has held there are two limbs to the ''M'Naghten Rules'', that the accused did not know what he was doing, or that the accused did not appreciate that what he was doing was morally wrong, in both cases the accused must be operating under a 'defect of reason, from a disease of the mind'. The High Court i
''R v Porter''
stated that the condition of the accused's mind is relevant only at the time of the actus reus
''Actus reus'' (), sometimes called the external element or the objective element of a crime, is the Latin
Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was ...
. In ''Woodbridge v The Queen'' the court stated that a symptom indicating a disease of the mind must be prone to recur and be the result of an underlying pathological infirmity. A ‘defect of reason’ is the inability to think rationally and pertains to incapacity to reason, rather than having unsound ideas or difficulty with such a task. Examples of disease of the mind include Arteriosclerosis (considered so because the hardening of the arteries affects the mind.
Canada
Criminal Code provisions
The defence of mental disorder is codified in section 16 of the ''Criminal Code
A criminal code (or penal code) is a document that compiles all, or a significant amount of, a particular jurisdiction's criminal law
Criminal law is the body of law
Law is a system
A system is a group of Interaction, interactin ...
'' which states, in part:
:''16. (1) No person is criminally responsible for an act committed or an omission made while suffering from a mental disorder
A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such features may be persistent, relapsing
In internal medici ...
that rendered the person incapable of appreciating the nature and quality of the act or omission or of knowing that it was wrong.''
To establish a claim of mental disorder the party raising the issue must show on a balance of probabilities
Burden of proof is a legal duty that encompasses two connected but separate ideas that apply for establishing the truth of facts in a trial before tribunals in the United States: the "burden of production" and the "burden of persuasion." In a lega ...
first that the person who committed the act was suffering from a "disease of the mind", and second, that at the time of the offence they were either 1) unable to appreciate the "nature and quality" of the act, or 2) did not know it was "wrong".
The meaning of the word "wrong" was determined in the Supreme Court case of '' R. v. Chaulk'' 3_S.C.R..html" ;"title="990

3 S.C.R.">990