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Handbook of Forensic Psychiatric Practice in Capital Cases


Te legal test in regard to ‘diminished responsibility’ in most common law jurisdictions is that a person 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 cause 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’.12 13


‘Abnormality of mind’ is further defined (in R v Byrne) as ‘a state of mind so different from that of the ordinary person that the reasonable man would term it abnormal’. Te term is also defined so as to include ‘the mind in all its aspects’, and so, in contrast with insanity, it can include any type of mental state abnormality or mental condition.


Tere is no psychiatric disorder that automatically qualifies as ‘abnormality of mind’ and so, whilst mental health evidence is essential to support the determination (R v Dix), it is ultimately that which the reasonable man would term ‘abnormal’.


Schizophrenia and paranoid psychosis, mood disorders and learning disability might be obvious qualifying disorders; however, personality disorder, pre-menstrual stress. post-natal depression, battered woman syndrome, alcohol dependence syndrome and post-traumatic stress disorder have, been accepted as a diagnosis that forms the foundation of all this defence.


A diagnosis of ‘substance dependence syndrome’ cannot be used as the relevant ‘abnormality of mind’ within the defence, unless it was such as to cause ‘irresistible impulse to take the first drink (or drug) of the day’, such that the intoxication ceases to be viewed as ‘voluntary’ (R v Tandy).14


Te ‘second limb’ of the test is not clearly ultimately for expert evidence comment, in that ‘mental responsibility’ is not a medical concept. However, clearly expert evidence will assist its legal determination. Tat is, an expert may properly describe the nature of the defendant’s likely abnormal mental state at the time of the killing. S/he may also properly describe how that abnormal mental state likely contributed to the ‘narrative’ of the offence, whilst leaving the jury to determine whether that ‘translates’ reasonably into substantial impairment of mental responsibility.


A further reason for not commenting upon ‘diminished responsibility’ per se is that there may be evidence in dispute, concerning likely symptoms (based upon witness evidence) or concerning the ‘narrative’ of the killing, which the jury will have to determine before deciding upon the relevance of any expertly described likely mental state abnormalities.


Te abnormality of mind that has been described should therefore be discussed in terms of emotional state, perception, cognition, consciousness and volition, plus the likely effects on behaviour. For example, if a person was in a state of depression with psychosis, then there may likely have been


12


Criminal Justice Act (NI) 1966 13


Prior to reform of the test, by way of the Coroners and Justice Act 2009, in England and Wales, S2 Homicide Act 1957; and Northern Ireland S5 Reform in England and Wales, under S52, Coroners and Justice Act, 2009, has substituted a much more ‘medically based’ definition of ‘diminished


responsibility’, written in terms of the defendant having been subject to ‘substantially impaired capacity to understand their own actions, or to exercise rational judgment, or to exercise self control’, ‘arising from a recognised medical condition’, which caused ... meaning was a significant contributory factor in


causing, the killing’, without any reference to ‘mental responsibility’ per se) 14


More recent case law has modified this stringent test somewhat, but its essence remains. 90


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