The defence of diminished responsibility
Scottish and English law on insanity was same in the sixteenth century, since “1674 a notion of partial insanity" to lessen and moderate the punishments" of the persons whose reasoning faculties were impaired.  Thus:
“Since the law grants a total impunity to such as are absolutely furious, it should by the rule of proportions lessen and moderate the punishments of such". 
Therefore “weakness of mind",  “a state of mind bordering on, though not amounting to, insanity"  or “partial insanity"  were allowed the accuse to avoid the sentence of murder. Walker asserts that, by 1909 the cases begin to use, the specific phrase “diminished responsibility".
“By the nineteen-thirties the stage had been reached at which the defense of insanity was rarely offered in a Scots court to a charge of murder. Either the accused was found “insane in bar of trial" or he pleaded diminished responsibility". 
2.1.4. In England Dissatisfaction With Mc’Naghten Rules.
In England, by 1883 from the judgment of the earlier case, dissatisfaction with the Mc’Naghten Rules (pronounced, and sometimes spelled, McNaughton) for insanity defence led to the recommendations for an alternate defence such as “diminished responsibility".  But this time this concept was not appreciated and again discussed in 1950 with regard to the capital punishment but the Royal commission (1949-53) rejected it too. In 1956 Heald Committee proposed this defense and later on the basis of this proposal sec. 2 of Homicide Act, 1957 was codified. 
Section 2 of Homicide Act, 1957 stated below:
“(1) Where a person kills or is party to the killing of another, he shall not be convicted of murder 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 or omissions in doing or being a party to the killing.
(2) On a charge of murder, it shall be for the defense to prove that the person charged is by virtue of this section not liable to be convicted of murder".
The effect of sec. 2 was to “take over the sort of case which previously would have been accepted by courts as within the Mc’Naghten Rules".  Moreover, studies have indicated that in its initial years was exceptionally effective, that a spacious variation of conditions were considered as satiate the interpretation of this Act while overall percentage of the people taken diminished or insanity did not vary. 
In U.S. The Diminished Responsibility Defense.
In U.S. this defense is known as diminished capacity. The diminished capacity principle is applicable to those who are mentally ill and unable to understand the consequences of their act at the time of crime. It is not applicable to every offence, it is only limited to the crime in the group of “specific intent", i.e. murder. All the American states have not the same view over diminished capacity. It is very controversial and even not available in a certain States. Some States have enacted the diminished capacity law while other States recognizes the defense of “Irresistible Impulse"; it is broader than diminished capacity. The conviction of manslaughter would be awarded on the successful admittance of the diminished capacity plea.
In California was the first state where the diminished capacity defense recognized first time in the case People v. Wells 
2.2 Relation of Diminished Responsibility To Insanity.
Insanity and diminished responsibility defense are linked at their ideological hip by men rea. So in order to understand the concept of diminished responsibility firstly, I should have to discuss the insanity defense. As in Pakistan we have the insanity defense for the accused that are suffered from some sort of mental illness and not diminished responsibility defense. At the end of this dissertation paper I will give some suggestion to amend the law on insanity with respect to diminished responsibility.
2.2.1. Under Islamic Law
The concept of “not guilty by reason of insanity" was first time introduced in the era of Prophet (PBUH). But the western world, nearly seven centuries ago, exonerated the individual on the basis of mental illness.  In Islam there is comprehensive procedure of compensation with respect of the loss occurred. While the persons who are “insane not liable for the loss".
In Islamic law, accused is to be considered a guilty of particular forbidden act or omission if he or she did that act or omission with malice intention. Thus, the Shariah invariably link agent’s act with his will or intention.
It was narrated by Umar Ibnu Kahattab (R) he said, the Prophet (s.a.w) said “Every act’s validity is depending on the intention of the doer". 
In another Hadith the Prophet (s.a.w) said
“Acts are dependent on the intentions and everyone will get his reward in consonance with his intention". 
However the seat of will is mind it means intention and decision. For instance, the Arabs when “wishing some one will, say may Allah (s.w.t) protect you, thus if a person proposes to do an act does it, he is intentionally guilt thereof". 
It was narrated by Abu Hurairah (R) he said,
“the Prophet (s.a.w) said, Verily Allah (s.w.t) does not notice into your appearance nor your wealth but He (s.w.t) notices unto your hearts and deeds". 
On the basis of these injunctions we can say that in declaring the liability of the offender for the application of the principle that acts are linked with intention, the Shariah considers not only the offence but also offender’s intention. 
2.2.2. Essentials of a Crime.
act must be done with free will;
ability to distinguish between right and wrong;
knowing that act is prohibited; and
to know the nature of the act.
Fundamental constituent of the crime is men rea without which there is no crime. Actus rea and mens rea both constitute crime.  It is based on the maxim “actus non facit reum nisi mens sit rea" it means one cannot be accused of guilty just because of one’s act unless mind be so guilty. In the case Swet v. Parsley Lord Diplock stated, “An act does not make a person guilty of a crime unless his be so guilty".  For instance in the case of insane person he may unaware of the gravity of his act and does not possess the required mens rea for a crime.
By 1884 Mc’Naghten case gives the basis of insanity law in England. Pakistan inherited the same from its ancestor. Section 84 of Pakistan Penal Code 1860, herein referred as (PPC), is based upon Mc’Naghten rule. In this research paper I will discuss the law of several countries especially U.K, U.S and India. I will compare the Pakistani law with other countries where it is possible.
In this research paper I make an attempt to distinguish between legal and medical insanity, since in the legal and medical sense the meaning of insanity are altogether different.
2.3. Insanity In A Legal Sense
Insanity has not been defined in the PPC. It can be described as unsoundness of mind which makes the person unable to comprehend the consequences of his act. It damaged the cognitive faculties to such an extent that one’s ability to distinguish between right and wrong completely damaged. The person whose reasoning capacity is not damaged to the required extent and able to know the aftereffects of his act cannot rely o this defense. In a legal sense a person who does not possess the necessary element of a crime i.e. mens rea is not held liable for his act and not punishable under the law. 
Following are such kind of persons who are “non compos mentis (not of sound mind)"
(1) an idiot – an idiot is one who from birth had defective mental capacity. This infirmity in him is perpetual without lucid intervals;
(2) one made so by illness – by illness, a person is made non compos mentis. He is therefore excused in case of criminal responsibility, which he acts under the influence of this disorder;
(3) a lunatic or a madman – lunatics are those who become insane and whose incapacity might be or was temporary or intermittent. A lunatic is afflicted by mental disorder only at certain period and vicissitudes, having intervals of reason; and
(4) one who is drunk – this is covered under PPC and IPC, s. 85.
Insanity in Medical Sense
Insanity in neuroscience is much broader than legal sense, it includes mental illness on the one hand, and it injures the cognitive capacity. On the other hand it also includes “mental disorder" with varied levels. Insanity generally includes idiots, lunatics, madman and all types of abnormalities.
2.4. Rationale for the Insanity Defence
The insanity defense is based on the general principle “that criminal behavior is punishable only when the actor is morally culpable or blameworthy".  An individual who suffered from mental illness or disorder may not know the nature of his act and cannot choose what is lawful or unlawful. In the case Holloway v. United States, the court succinctly stated: “Our collective conscience does not allow punishment where it cannot impose blame". 
Criminal law recognizes certain defences that excludes the whole or diminish the criminal liability, when individual does an act voluntarily or without criminal intent.  But the question which needs to be determined is that what constitute the insanity.
2.5. Constituent factors of Insanity Defence
For common man insanity means something equivalent to mental illness and it require psychiatric treatment. But for a psychologist and psychiatrist insanity mean “mental disorder", “mental defect" and “mental disease". 
“The Halsbury’s Laws of England explain that where on a criminal charge, it appears that, at the time of the act or omission giving rise to the offence alleged, the defendant was laboring under a defect of reason owing to a disease of mind so as not to know the nature and quality of his act, or, if he knew this, so as not to know that what he was doing was wrong, he is not regarded in law as responsible for the act. The question whether, owing to a defect of reason due to the disease of the mind, the defendant was not responsible for his act is a question of fact to be determined by the jury. Where the jury finds insanity is made out the verdict takes place in the form of not guilty due to insanity". 
2.5.1. Essential of Insanity Defence
Three things need to be proved where insanity defense is pleaded:
(1) Mental disorder must be present in order to plead the insanity defense. According to Lord Denning “any mental disorder which has manifested itself in violence and is prone to recur is a disease of the mind. At any rate it is the sort of disease for which a person should be detained in hospital rather than be given an unqualified acquittal". In the landmark case R v. Sullivan, Lord Diplock gives the definition of the disease of mind, “mind in the Mc’Naghten rules is used in the ordinary sense of the medical faculties of reason, memory and understanding. If the effect of the disease is to impair these faculties so severely as to have either of the consequences referred to in the latter part of the rules, it matters not whether the etiology of the impairment is organic, as in epilepsy, or functional, or whether the impairment is itself permanent or is transient and intermittent, provided that it subsisted at the time of commission of the act";
(2) “The disease of the mind must give rise to a defect of reason. The reasoning power of a person must be impaired. The defendant must show that he was suffering from such defect of reason that he did not know the nature and quality of the act he had committed, or if he did know, that he did not know that what he was doing was wrong. If the accused is relying on the second limb, he must show proof that he did not know that it was legally wrong; and as a result, he either did not know that what he was doing was wrong; and
(3) If the accused’s defect of reason is to be effective in establishing the defense of insanity, the insanity must affect his legal responsibility for his conduct as such he is not able to realise that what he was doing is wrong. Wrong here means something that is contrary to law". 
2.6. Evolution of the Insanity Law
After a long trial and tests the insanity defense is developed.
In 1724 the Arnold case articulated the Wild Beast test, Justice Tracy a judge of 13th century in King Edward’s Court laid down the basis of the insanity defense and directed the jury to exempt the individual if the insanity defense is established by the accused. Justice Tracy defined the madman, “a man that is totally deprived of his understanding and memory, and doth know what he is doing, no more than an infant, than a brute, or a wild beast, such a one is never the object of punishment".
In the case R v. Madfield, the Good and Evil test was articulated, the test is “the ability to distinguish between good and evil". There was a charge of treason, for an attempt to murder the Kind, made against the defendant, the defense counsel argued “that the accused was not able to differentiate between good and evil and ‘wild beast test’ was not reasonable". And his plea was accepted.
2.6.3. The Mc’Naghten Rule
The English law on insanity is based on the Mc’Naghten rules laid down in the Mc, Naghten case,  in this case the “Mc 'Naghten was a Scottish woodcutter who murdered the secretary to the Prime Minister, Sir Robert Peel, in a botched attempt to assassinate the prime minister himself. Mc 'Naghten apparently believed that the prime minister was the architect of the myriad of personal and financial misfortunes that had befallen him. During his trial, nine witnesses testified to the fact that he was insane, and the jury acquitted him, finding him not guilty by reason of insanity".  Since then the Mc’Naghten rule become widely accepted.
Mc’Naghten rules mainly deal with the defect of reason. Thus the individual who suffered from the “disease of mine’ and owing to the disease he didn’t know either:
“The nature and quality of the act the person was committing; or
That what the person was doing was wrong". 
This rule was widely criticized by Royal commission (1949-53)  and the strata of the society i.e. lawyers and doctors. They “have contended that the Mc’Naghten test is based on the entirely obsolete and misleading conception of nature of insanity, since insanity does not only affect the cognitive faculties but affects the whole personality of the person including both the will and the emotions". Mc’Naghten rule ignore one important factor that owing to the mental illness sometime a person commit an act on having the knowledge that the law forbids it.  6 Commission proposed that Mc’Naghten rule should be modified. Albeit its practice is still continue.
2.6.4. Irresistible Impulse Test
Mc’Naghten rule had become the widely accepted in America by 1851. Despite it subjected to criticism by federal court and developed a new test “Irresistible Impulse Test" with some addition in the Mc’Naghten rule. Under this test “the defendant knew right from wrong, nevertheless acted from an irresistible and uncontrollable impulse; the defendant lost the power to choose between right from wrong; the defendant’s free agency to avoid doing the act was destroyed; and the defendant’s will has been so completely destroyed that his actions are beyond his control". 
This test is also criticized that: “the irresistible impulse test unduly broadened the insanity defence; and the irresistible impulse test’s focus on a defendant’s sudden, impulsive loss of control ignored the possibility of a long-term, gradual loss of control". 
2.6.5. The Durham or “Product" Test
In this case Durham v. United States  Court of Appeal devised a new test to determine the insanity. Before discussing the test it would not be out of place to mention the brief facts of the case. Monte Durham was accused of housebreaking and pleaded the defence of mental illness. It was accepted on the ground of the previous history of his mental illness. While asserting this defense on the “fundamental principle that thought processes is an integrated, functional unit," the Court articulated the test given below:
“an accused is not criminally responsible if his unlawful act was the product of mental disease or mental defect."  There must be a sound proof that owing to “mental illness" the defendant is not liable.  This test was criticized because of the ambiguity in term “product".
2.6.6. Model Penal Code Test.
This criticism founded the basis of American Law Institute; it propounded the Model Penal Code Test, it is stated below:
“A person is not responsible for criminal conduct if at the time of such conduct as a result of mental disease or defect he lacks substantial capacity either to appreciate the criminality of his conduct (the cognitive capacity prong) or to conform his conduct to the requirements of the law (the volitional capacity prong)".  This test equalizes the volitional and cognitive function of mind. Though the essential requirement is there must a material impairment.  This test has nothing to do with the “unrealistic" necessity of complete impairment, a requirement of Mc’Naghten and “irresistible impulse test". 
It was propounded by the supporters that the Model Penal Code test “is more consistent with the available medical testimony regarding insanity, is less rigid, and is simpler for a jury to apply and understand than other tests."  However, it was largely accepted notwithstanding of the criticism on its volitional prong and its “unduly broad and fuzzy phrase ‘lack of substantial capacity’" 
2.7. Relation of Diminished Capacity to Insanity under U.S. Jurisdiction.
North Carolina courts in the case State v. Shank  , considered that the diminished capacity and insanity are not same. In State v. Silvers, “the defendants may be found insane in North Carolina if, at the time of the offence, they were incapable of knowing the nature and quality of their actions or that their actions were wrong".  On the contrary the defendant lacked the “necessary state of mind" for conviction in the diminished capacity defense.  In Shank, court accepted the defense of mental disorder, “psychogenic amnesia" the illness that make the defendant unable to “premeditating or deliberating", indicates that the court may allow the diminished capacity defense in addition to insanity defense.
State of mind defences has affirmed by the Supreme Court, such as “insanity and voluntary intoxication, are not mutually exclusive. They may coexist in the same case and be considered, jointly and severally, by the jury." 
2.8. Applicability to Different Offences
In a murder case the prosecution is required to prove that the defendant acted with the malicious intention. The proof of the murder of Ist degree is different from murder of 2nd degree. To prove the murder of Ist degree prosecution also required to prove additional element of “premeditation and deliberation". Where the constituent element of the murder of ist degree did not prove then the defendant cannot be punished for that offence. The courts in North Carolina (N.C) consider the “specific intent" an essential element of “premeditation and deliberation" and hence essential constituent of the murder of Ist degree. The Supreme Court reaffirmed in the case State v. Holde, the “specific intent" to murder is an “essential constituent of the elements of premeditation and deliberation."
The accused cannot escape the liability of a criminal act even if “premeditation and deliberation" or the “specific intent" does not prove and the accused is still accountable of the murder of 2nd degree for which only the proof of malice is required by the Supreme Court. 
2.8.2. Offences other than Murder
North Carolina courts are still uncertain whether the diminished capacity defences accessible to the other offences other than the murder i.e. burglary, felony and larceny. If this would be the case conviction could easily be prevented in other offences. In the case of voluntary intoxication this issue has been discussed as it has similarity with the diminished capacity defense. In both defences the defendant does not have the required “state of mind". 
In order to avail the defense of voluntary intoxication it is required that the offence in issue required specific intent to be proved. There are two kinds of offences____ “not requiring specific intent" and “requiring specific intent".
Offences “Not Requiring Specific Intent"
It has been established that voluntary intoxication in not a defense in such offences where “specific intent is not required". There is no generally accepted rule to identify the crimes for which “specific intent" is required. The distinction was made by LaFave in the two types of intent by defining “general intent as an intent to do the physical act . . . which the crime requires" and specific intent as “some intent in addition to the intent to do the physical act which the crime requires".  These categories of offences have been criticized by LaFave and other critics. “Mental element" required for many offences are not applicable precisely. For example, “second-degree murder requires proof of malice, of which the Supreme Court has recognized at least three different kinds,  while arson requires proof that the defendant acted willfully and maliciously". 
“Commentators have also criticized the specific intent/general intent approach as an artifice, without logical coherence or empirical support, which courts have used to exclude relevant state of mind evidence in general intent cases". 
Offences “Requiring Specific Intent"
North Carolina courts permitted the “voluntary intoxication" defense for the offences those “require specific intent". “Many offences other than first-degree murder require proof of specific intent, including burglary (intent to commit felony or larceny), attempt crimes (intent to commit crime), and assault with a deadly weapon with intent to kill (intent to kill)". 
However, it is clear from the above discussion that the courts in North Carolina will permit the Diminished capacity and voluntary intoxication defences with the same frequency as in both defences mental element i.e. mens rea is not present.
2.8.2.a in order to clarify it the researcher resort to some older case where the court employed the element of mental illness to convict the offender.  Though these cases reflect the practice of taking into account the extenuating circumstances in order to escape the mandatory sentence rather diminished responsibility defense. It can be traces in some modern cases. 
2.8.2.b. In the case HM Advocate v Blake the accused made and attempt for murder and pleaded the insanity defense. The judge instructed the jury if the diminished responsibility had been established by the accused their decision would be “guilty of assault under deletion of attempted murder on the ground of diminished responsibility."  Though the accused mental state had taken in account by the jury but did not mention whether the diminished responsibility defense is applicable only in the murder cases.
Lord Justice General Clyde stated: "Any mental or pathological condition short of insanity – any question of diminished responsibility owing to any cause, which does not involve insanity – is relevant only to the question of mitigating circumstances and sentence. An argument was presented to us in regard to diminished responsibility. But diminished responsibility is a plea applicable to murder. It is not open in the case of a lesser crime such as culpable homicide or of a contravention of section 1 of the Road Traffic Act, 1960". 
Lord Justice General Emslie said: "proof of the mere effects of such intoxication, whatever their degree, cannot in our law support a defense of diminished responsibility – a defense available only where the charge is murder and which, if it is established, can result only in the return of a verdict of guilt of the lesser crime of culpable homicide". 
2.11. Frequency of the Diminished Responsibility Defense.
As the researcher find no research data showing the frequency of diminished responsibility defense. In 1984 a study paper was published by the Susane Dell,  “Accordingly, it was decided to examine a sample of diminished responsibility cases for the five years from 1997 to 2001. In doing so it must be pointed out that it has not been possible, for a number of reasons, to gain access to all the relevant cases. The Homicide Statistics reveal that in the five year period between 1997 and 2001 there were around 171 successful diminished responsibility pleas".  This paper shows that 157 cases availed this defense including 21 cases were not successful, however, it does not claim to cover the all successful cases. Nevertheless this study paper is useful as no other study is available showing unsuccessful cases, as far as known.
In New South Wales, the total percentage of people not guilty on the basis of mental illness is short. Research shows only eight acquittals during the period of 1990-1992.  It is not easy to plead the insanity defense as it involves a heavy burden of persuasion that’s why diminished responsibility defense might be pleaded (particularly if it is admitted).