Diminished Responsibility


Diminished Responsibility (DR)

Notes: Diminished Responsibility notes Diminished Responsibility notes  Diminished Responsibility Diminished ResponsibilityEvaluation of Diminshed Responsibility Evaluation of Diminshed Responsibility


Task: Complete the following worksheet worksheet using the website, A2 law books and other relevant resources. Use the case note on R v Foye R v Foyeto help you. 


Watch a recent report on a case where the D has argued Diminished responsibility:




The defence is only available for the offence of murder. It is a statutory defence that if successful reduces a verdict of guilty of murder to one of guilty of manslaughter. It is therefore called a partial defence, as it does NOT result in an acquittal. The defence contained in the Homicide Act 1957 but has now been amended by the Coroners & Justice Act 2009.


The defence is based on the D’s lack of mental capacity at the time of the killing. The D must raise the defence and must also prove he suffered DR so un unusually the burden of proof is on the D. This is because the D has access to all the medical records. The D only has to prove the defence on a balance of probability. This makes it a lot easier to prove a lack of mental capacity from the evidence.


Definition: A person (“D”) who kills or is a party to the killing of another is not to be convicted of murder if D was suffering from an abnormality of mental functioning which:


a.              Arose from a recognised medical condition

b.              Substantially impaired D’s ability to do one or more of the things mentioned in subsection (1A), and

c.              Provides an explanation for D’s acts and omissions in doing or being a party to the killing.


Subsection (1A) those things are:


a.              To understand the nature of D’s conduct;

b.              To form a rational judgement;

c.              To exercise self-control.


(1B) For the purposes of section 2(1)(c), an abnormality of mental functioning provides an explanation for D’s conduct if it causes, or is a significant contributory factor in causing D to carry out that conduct.


How the defence is raised


D gives the judge evidence of DR. 80% of those raising the defence are allowed the defence so the judge reduces murder to manslaughter. Some DR cases are not allowed to be raised as the judge believes the evidence is not sufficient, e.g. Yorkshire ripper case. See the documentary below:


If the judge believes there is evidence of the defence but isn’t sure D has proof on balance of probability then it will be sent to trial, where P must prove murder and D must prove DR. The defence can be raised at any time, even at appeal stage.


1.   Abnormality of mental functioning:


According to the case of Byrne (1960): The appellant murdered a young girl staying in a YWCA hostel. He then mutilated her body. He did so as he was suffering from irresistible impulses which he was unable to control.


Held:  an abnormality of mental function is defined very widely:


‘Abnormality of mind...means a state of mind so different from that of ordinary human beings that the reasonable man would term it abnormal’

Gomez (1964):  The abnormality doesn’t have to permanent or have existed from birth as long as it existed at the time of the killing.


2.   Recognised medical conditions


Coroners and Justice Act 2009 recognises that there are many different existing lists which classify accepted physical, psychiatric and psychological conditions. Foremost among these are the World Health Organisation’s international classification of diseases, and the American Psychiatric Association’s diagnostic and statistical manual of mental disorders. If a jury accepts that, at the time of the killing, a defendant was suffering from a condition included in one of these lists, then the test in (a), the definition, will be met. There may well be new or emerging conditions which are recognised, but which are not on one of the accepted lists. In such a case, the defence can call an acknowledged specialist whose work has been validated. It will then be up to the jury, properly directed, to consider this evidence.


Depression:                                        R v Gittens

Irresistible Impulses:                       R v Byrne

Battered wife Syndrome                  R v Ahluawalia

Alcohol Dependency Syndrome:       R v Stewart

Paranoia                                             R v Simcox

Adjustment disorder                          R v Dietschmann


Can also include, Post natal depression, pre menstrual tension, extreme jealously as a medical condition and Asperger’s.



3.   Substantially impairs:




R v Lloyd 1967: D strangled his wife. Medical evidence was that he suffered from reactive recurrent depressions, and his mental responsibility was impaired by that abnormality to some extent, not to any substantial degree - it was not as low as minimal but, on the other hand, it was not substantial.


Held:  Substantial does not mean totally impaired. Substantial is more than minimal or trivial. It is upto the jury to decide whether the D’s responsibility was impaired so much by the medical condition to kill.








4.   Diminished responsibility and being intoxicated


If someone is drunk and became intoxicated of their own free will this cannot be a defence.


Only if the D can show their intoxication was involuntary due to a medical condition can the defence be used. Not all alcoholics have a recognised medical condition of this sort.


R v Tandy: The defendant was an alcoholic. She killed her 11 year old daughter by strangulation after the daughter told her she was being sexually abused by her step father. On the day of the killing the defendant had drunk almost a whole bottle of vodka which was stronger then her normal drink of cinzano. At her trial she was convicted of murder and appealed.


Held: If the defendant merely failed to resist the impulse to drink, and only the first drink was voluntary, she could not claim diminished responsibility.


5. Being intoxicated and also having a recognised mental condition

R v Gittens 1984: : D was suffering from depression. During a visit home from hospital he argued with his wife and beat her to death and then raped and killed his stepdaughter. At the time of the offence he had been drinking and taking drugs for depression.

Held: The CA said that the jury should be told to ignore the effects of any alcohol that was drunk voluntarily by the D. The jury should look at the effects of the D’s depression to see if this substantially impaired the D’s ability to do 1 or more of the listed things in the act. Alcohol drunk due to the medical condition can be taken into account in impairing the D’s mental condition.

R v Dietschmann 2003 HL: The situation here is did the voluntary consumption of alcohol cause the D’s medical condition to be aggravated enough to substantially impair and kill?  The direction to the jury is simply did the D’s medical condition substantially impair the D enough to kill, regardless of how the condition arose, i.e. due to drinking. If there is a substantial impairment then this is enough to satisfy this element of the defence regardless of voluntary intoxication.


6. Having a disease brought about by Alcoholism – Alcohol Dependency Syndrome


R v Stewart 2009: If the D’s alcoholism has caused the brain to be altered physically so that they can no longer resist drinking alcohol this is a recognised medical condition, alcohol dependency syndrome (ADS). However the jury must work out whether the D’s drinking was involuntary before considering ADS as a substantial impairment by looking at the evidence. For example can D decide for himself when to drink and for how long? If they cant it indicates a substantial impairment.


7.Impaired to do one or more things that provides an explanation for the killing


As long as D can show the mental functioning caused by the medical condition caused one or more of the 3 things listed to be provide an explanation for the killing then the jury can allow the defence. Remember it is the lower level of evidence, on balance (51%), that the D has to show. Your problem solving should take this into account.


Understand own conduct: e.g. Stewart ADS and alcohol made D delusional

Form a rational judgment: e.g. Simcox paranoia meant he perceived threats that weren’t really there

Exercise self control: e.g. Byrne knew he was killing but his condition meant he couldn’t resist the impulse to do this.


Evaluation of Diminshed Responsibility


Task: Watch the video and make a note of the medical conditions and cases mentioned. What are the arguments for and against the videos view that women are treated more favourably than men with regards to the defence of Diminshed Responsibility?




Criticisms of the defence of Diminished Responsibility




The main problems with this defence as defined by the Homicide Act 1957 were that:


  1. The words of s2 of the Homicide Act were not clear as to what constitute the causes of abnormality of mind.


  1. Unlike other defences, the burden of proof is on the defendant.

  2. Defence does not allow for developmental immaturity.


Burden of proof


In the case of provocation, (now ‘loss of control’) the defence only has to raise the issue, and the prosecution has to disprove it. This is not the case with diminished responsibility, where the defendant has to show, on the balance of probabilities, that there were circumstances that would warrant that defence. This may be in contravention of Article 6 (2) of the European Convention of Human Rights which states that ‘everyone charged with a criminal offence shall be presumed innocent until proven guilty according to the law’. Making the D prove diminished responsibility could be considered a breach of this right to be presumed innocent.


Abnormality of mind


Cases over the years have shown significant differences of opinion between doctors as to what conditions fall within this definition. They also raised the question as to whether ‘substantial impairment of mental responsibility’ should be a matter settled necessarily by the medical profession. Should psychiatrists be asked to give their opinions on what are felt by many people to be essentially moral issues?


The Coroners and Justice Act 2009 retains the partial defence of Diminished Responsibility but makes it a condition that the recognised medical condition must cause the abnormality of mind, with the phrase being undefined in the Act.


With such a link now required between a “recognised” medical condition and being able to raise the new defence the risk is new and unrecognised conditions may not be accepted as having sufficient medical authority to be allowed to be put to the jury. This means cases such as Battered Wife Syndrome and other emerging conditions risk being rejected as a recognised condition until doctors formally acknowledge the condition. This could risk the law stagnating or D’s being unable to use the defence simply because they are the first (as in Ahluwalia) to be diagnosed.


Defence does not allow for developmental immaturity


The Law Commission suggested this being allowed for those who from birth or an early age were mentally deficient or under developed in their brain (think of any unreasonable teenager) and as a result killed. This would become a recognised medical condition for those upto 18. However, the government rejected the idea as they felt that anyone with developmental immaturity would also have another recognised medical condition such as autism and this would allow the appropriate defence.


The result of pleading this partial defence successfully will still be a conviction for manslaughter instead of murder.

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