Citation(2005) 17 SAcLJ 793
Published date01 December 2005
Date01 December 2005

The defences of diminished responsibility and provocation do not absolve the killer of all culpability. Both excuses, if successfully argued, only serve to reduce the killer’s culpability from that of a murderer to that of an offender who commits culpable homicide not amounting to murder. Nonetheless, there is a substantive difference in the nature of the two excuses. Diminished responsibility requires a more subjective enquiry into the killer’s state of mind at the time of the killing, making it an exclusive defence unique to the defendant. Provocation, on the other hand, focuses on an objective enquiry into the reason why the killer lost self-control. The aim of this article is to analyse how the development of these two excuses in Singapore has exposed their innate differences.

I. The development of diminished responsibility in Singapore

1 Within the sphere of diminished responsibility, law and psychiatry work together by matching wrongful acts with the actor’s appropriate level of culpability. These two disciplines help determine the actor’s mental responsibility at the time the act was performed and assign an accurate level of culpability to the actor. The three limbs that need to be satisfied before the diminished responsibility defence can be successfully applied are:

(a) the offender must have been suffering from an abnormality of mind; and

(b) this abnormality of mind must have been caused by:

(i) a condition of arrested development of mind;

(ii) a condition of retarded development of mind;

(iii) any inherent causes; or

(iv) induced by disease or injury; and

(c) the abnormality of mind caused by any one of the above [(b)(i) to (b)(iv)] must have substantially impaired the offender’s mental responsibility as regards the offender’s acts and omissions in causing the death or being a party to causing the death.1

2 If the accused does not satisfy any one of these three limbs, he will not be able to take benefit of the defence. The burden of proving each limb lies on the Defence and the level of proof is only one of “a balance of probabilities”.2

3 The authoritative judicial interpretation of the boundaries of these three limbs is found in the judgment of Lord Parker CJ in the case of Regina v Byrne.3 His Lordship’s judgment, cited with approval by the Singapore Court of Appeal in Chua Hwa Soon Jimmy v PP,4 provided the scope of each of the three limbs.

A. “Abnormality of mind” limb

4 The classification “abnormality of mind” is a reasonable man’s classification (ie, the question to ask is, “Would a reasonable man think of the offender’s state of mind as so different from that of ordinary human beings?”). This is not a scientific classification but one drawn from the lay

and reasonable man’s mind.5 In coming to the decision as to whether there was an abnormality of mind, our judges are entitled to treat medical evidence as guides for their decisions.6 This is an entitlement, in the same way that it is an entitlement for the judges to form their own conclusions if presented with evidence that conflicts with the opinion drawn from the medical evidence.7 These other facts to which the judge is privy and upon which he can rely include the acts and demeanour of the accused surrounding the time of the killing, and any other conflicting psychiatric opinion.8

B. The “cause” limb

5 Nonetheless, the aetiology of the abnormality of mind (ie, how it arose, how it was caused or how it was induced) is solely a matter for the

medical experts.9 Thus, the satisfaction of the second limb depends solely on the conclusion of medical men.10

C. The “substantial impairment” limb

6 The judge must consider the extent to which the offender’s mind is answerable for his physical acts. Such consideration must include an analysis of the offender’s ability to exercise his will over his acts that led to the killing. The question as to whether the offender’s mental responsibility was substantially impaired is a question for the judge. While medical evidence relating to the presence of mental impairment is important and constructive, the finding of the judge can legitimately oppose the conclusions of the medical men.11

7 In coming to his conclusion as to whether the accused’s mental responsibility was substantially impaired, the judge is guided by the following distinction: In a case where the abnormality of mind is one which affects the accused’s self-control, the step between “he did not resist his impulse” and “he could not resist his impulse” is an important one. The latter is more favourable to the accused.

D. Judicial interpretation of substantial impairment

8 In the Jimmy Chua case,12 Yong Pung How CJ provided clear direction that “substantial” was a finite benchmark but one which also possessed the attribute of degree. Yong CJ ruled:13

Turning to exception 7 to s 300 of the Penal Code, the determination of whether impairment of mental responsibility was substantial would involve a question of degree, to be tested against and ascertained from all the evidence of each individual case. That was why in R v Lloyd[1967] 1 QB 175 at pp 178—179, the English court gave only a broad direction to the jury:

[Y]our own common sense will tell you what [substantial] means. This far I will go. Substantial does not mean total, that is to say the mental responsibility need not be totally impaired, so to speak, destroyed altogether. At the other end of the scale substantial does not mean trivial or minimal. It is something in between and Parliament has left it to you … to say on the evidence: was the mental responsibility impaired, and if so, was it substantially impaired?14

The direction above may be broad, but it was useful for it at least set out the markers at the extremities of the scale which [the Court of Appeal] had to work within.

9 Importantly, the Court of Appeal in the Jimmy Chua case relied on the acts of the accused, his demeanour and his presence of mind at the time of the alleged offence to assist itself in coming to a conclusion about whether the offender was in fact suffering from substantial impairment of mental responsibility. The following extract from the judgment is insightful:15

On the totality of the evidence, we concluded that the appellant could have restrained himself, even if we accepted that he was commanded by a voice. His abnormality of mind (if any) was not such as to substantially impair his mental responsibility for the offence committed. After all, he had the presence of mind to try and tie the deceased up

when assaulted; to avoid electrocution by using the telephone cord instead of pulling the plug; to look for the keys to make his escape; to put on his boots before leaving the crime scene; and to dispose of his bloodied clothes. His behaviour immediately after the murder was also inconsistent with a person who claimed to be out of control. Therefore, the entire episode, in our judgment, demonstrated that the appellant’s mind was not substantially impaired as to absolve him of mental responsibility for his foul crime. [emphasis in original]

10 The entitlement of the court to look at the acts, demeanour and presence of mind of the accused at or around the time of the alleged offence16 in order to come to a more thorough decision on the presence or absence of “substantial impairment” was further expressed in Tengku Jonaris Badlishah v PP,17Zainul Abidin bin Malik v PP,18Contemplacion v PP19 and Mohd Sulaiman v PP.20

11 While the psychiatrists dictate the fulfilment of the second limb, it is for the judge to conclude whether the first and third limbs have been satisfied. Thus, even where the prosecution and defence psychiatrists agree, for example, that voluntary substance abuse by the accused has brought about a disease21 which caused an abnormality of mind,22 the judge is at total liberty to reject the fulfilment of the third limb. This was

the exact scenario in the case of PP v Zailani bin Ahmad23 where both the defence and prosecution psychiatrists agreed that the accused was suffering from acute intoxication with hypnotics. The accused, a seasoned drug addict, had taken 12 Nitrazepam pills (belonging to the Benzodiazepine class of drugs) before killing a Geylang rent collector. The general practitioner who prescribed the drugs testified that he had examined the accused, diagnosed him as suffering from insomnia, and prescribed him the sleeping pills the day before the killing. It was this evidence that prompted the psychiatrists to take a keen look at whether the accused was suffering from an abnormality of mind, brought about by an overdose of sleeping pills, at the time he killed the rent collector.

12 Both psychiatrists agreed that he was suffering from an abnormality of mind and that it was caused by a disease, as classified under under F13.0 of the International Classification of Diseases, vol 10. The learned trial judge agreed with the unanimous psychiatric evidence, and found that limb one was fulfilled. As regards the second limb, the trial judge was bound to accept the medical evidence that acute intoxication with hypnotics (the abnormality of mind) was indeed a disease. Thus, the second limb was fulfilled.

13 At the third limb, there was a difference in opinion between the defence and prosecution psychiatrists. The former opined that the abnormality of mind caused a further “temporary paradoxical stimulant effect” which in turn substantially impaired the accused’s mental responsibility at the time of the killing. The prosecution psychiatrist disagreed, stating that a paradoxical stimulant effect was inconsistent with the facts surrounding the case.

14 The learned judge ruled that the accused’s attempt to steal from the deceased’s chest of drawers immediately before the time of the killing and the fact that the accused continued his attempt to steal immediately after the time of the killing showed that the accused’s...

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