Diminished Responsibility and the Mandatory Death Penalty in Drug Trafficking Cases:
Roszaidi bin Osman v PP  SGCA 75
I. Executive Summary
In Roszaidi bin Osman v PP  SGCA 75, the Court of Appeal (“CA”) considered whether the appellant, Roszaidi bin Osman (“Roszaidi”), who had previously been convicted of trafficking in a controlled drug under section 5(1)(a) of the Misuse of Drugs Act (Cap 185, 2008 Rev Ed) (“MDA”) and accordingly sentenced to death under section 33 of the MDA was eligible to be re-sentenced to life imprisonment instead.
The basis of Roszaidi’s sentencing appeal was section 33B(1)(b) of the MDA, which requires the court to impose a sentence of life imprisonment in lieu of the death penalty for drug trafficking under the alternative sentencing regime, if the two requirements of sections 33B(3)(a) and 33B(3)(b) of the MDA are met. These are: that the accused is proven to merely be a courier within the meaning of section 33B(3)(a)(1) and that he was suffering from an abnormality of mind that substantially impaired his mental responsibility for the offence.
Roszaidi’s sentencing appeal had first been heard by the General Division of the High Court (“HC”), which held that the Roszaidi was not eligible for the alternative sentencing regime as he had not shown that he was suffering from an abnormality of mind which substantially impaired his mental responsibility under section 33B(3)(b). Roszaidi appealed against the HC’s judgment.
In a rare split 3-2 decision, the CA overturned the HC’s judgment. Roszaidi was instead sentenced to life imprisonment. Chief Justice Sundaresh Menon, Justice Judith Prakash and Justice Belinda Ang (collectively, “the Majority”) found that Roszaidi’s major depressive disorder (“MDD”) and substance use disorder (“SUD”) had substantially impaired his mental responsibility for his acts. These disorders together materially affected his ability to resist the urge to consume drugs, thus materially influencing his decision to traffic drugs as a means of feeding his drug habit. His MDD and SUD also influenced his impaired his mental responsibility for the act of trafficking itself, which was essentially his passing of the drugs in question to his then pregnant wife.
In contrast, Andrew Phang Boon Leong JCA and Steven Chong JCA (collectively, “the Minority”) upheld the HC’s decision. They rejected Roszaidi’s claim that his MDD had exacerbated his SUD, finding no causal link between his MDD and SUD. They then considered that Roszaidi’s MDD alone had neither sufficiently impaired his rational judgement in his decision to traffic drugs, nor his ability to exercise rational judgement over his actions in relation to the specific act of trafficking itself.
II. Material facts
Roszaidi had been a heavy user of drugs from a young age. He would subsequently be plagued by drug-related problems for most of his adult life, being convicted on multiple occasions of possessing, consuming, or trafficking illegal drugs.
Whilst serving his sentence in prison for being in unauthorised possession of diamorphine in 2014, Roszaidi’s father passed away. Roszaidi managed to largely abstain from consuming drugs for a year or more immediately after his release from prison, but either resumed or escalated his drug consumption in May 2015. At this time, his mother and grandmother died. These bereavements triggered his MDD. Shortly after these bereavements, Roszaidi quit his job. Further, his rate of drug consumption (of heroin, methamphetamine and dormicum) escalated.
Shortly after, Roszaidi began delivering drugs for a man named Is Cangeh. Lacking money to buy drugs for himself, Roszaidi instead took various drugs from the consignments that he delivered for his personal consumption to feed his drug addiction.
On October 6, 2015, Roszaidi was shopping with his wife and their daughter. While out, he received a call from Is Cangeh regarding collecting some drugs. Together with a friend, he then proceeded to collect some drugs from two other parties, including two packets containing not less than 32.54g of diamorphine (the “Drugs”). While waiting for some time for a call from the person to whom he was meant to deliver the drug consignment, Roszaidi called his wife and told her that he needed her to “come down to take something” from him, and for her to take along a plastic bag, without informing her what he was giving her. He subsequently handed her the Drugs. This act of passing the Drugs to his wife constituted Roszaidi’s offence of trafficking. The three (Roszaidi, his wife, and the friend) were arrested by Central Narcotics Bureau (“CNB”) officers later that night.
Roszaidi was subsequently charged with trafficking in a controlled drug under section 5(1)(a) of the MDA. As section 33B(1)(b) was not then pleaded, he was initially sentenced to the mandatory death penalty under section 33 of the MDA. He appealed against the conviction and sentence. His appeal against conviction was dismissed by the CA in Mohammad Azli bin Mohammad Salleh v Public Prosecutor and another appeal and other matters  1 SLR 1374 (“Azli”), as it was clear that Roszaidi had committed the offence of drug trafficking by knowingly transporting the Drugs. Regarding his appeal against his sentence, however, the CA remitted his case to the HC for consideration of certain issues concerning Roszaidi’s abnormalities of mind (discussed below).
The HC then held that Roszaidi was not eligible for the alternative sentencing regime. After considering the expert evidence of the two psychiatric experts who examined Roszaidi and gave expert evidence in the proceedings – Dr Jacob Rajesh (“Dr Rajesh”) who was the Defence’s expert, and Dr Bharaj Saluja (“Dr Saluja”) who was the Prosecution’s psychiatric expert – the HC held that Roszaidi’s MDD and SUD constituted an abnormality of mind. However, though the HC found that his MDD arose from an inherent cause, it held that his SUD did not. It rejected Dr Rajesh’s opinion that Roszaidi’s MDD had formed the “underlying substrate” for his SUD and that the two conditions had operated in a “synergistic” manner (the “Synergy Claim”).(2)
Further, the HC considered that Roszaidi’s MDD was only of mild severity and accepted that Roszaidi’s conduct at the time of the offence demonstrated that he had been able to exercise “multiple functions in the brain” such as planning, executing a plan, and understanding instructions from others. Hence, Roszaidi had not established that his MDD had substantially impaired his mental responsibility for his offences. Roszaidi then appealed against the HC’s judgment.
It had already been established in Roszaidi’s appeal to the CA against his conviction in Azli that he was a courier under section 33B(3)(a), i.e. he had merely delivered the Drugs on Is Cangeh’s directions. Thus, the CA focused here on whether Roszaidi satisfied the requirements of section 33B(3)(b) of the MDA, i.e. that he was suffering from an abnormality of mind that substantially impaired his mental responsibility for the offence.
The prior case of Nagaenthran a/l K Dharmalingam v Public Prosecutor and another appeal  2 SLR 216 had established that for this defence to apply, three limbs (or requirements) had to be established on a balance of probabilities (the “Nagaenthran test”):
(i) the accused was suffering from an abnormality of mind (the “First Limb”);
(ii) the abnormality of mind arose from either:
(iii) the abnormality of mind substantially impaired his mental responsibility for his acts and omissions in relation to his offence (the “Third Limb”).
There was no dispute that the First Limb was satisfied, as it was accepted that Roszaidi was suffering from MDD and SUD at the time of the offence. Therefore, the appeal pertained only to the Second and Third Limb, focusing on whether Roszaidi’s SUD (along with his MDD) arose from an inherent cause, and whether his SUD and MDD had operated together to substantially impair his mental responsibility.
A. The Majority Judgment
(1) The Second Limb
The CA first noted that the Second Limb was intended to be applied restrictively, to limit the application of section 33B(3)(b) to accused persons suffering from “recognised and established psychiatric conditions”, and to “exclude abnormalities of the mind that arose from other sources” such as heightened states of emotion or intoxication “that are not beyond the accused person’s control”. With these principles in mind, the CA noted that there was no dispute that Roszaidi’s MDD arose from an inherent cause. The question was whether Roszaidi’s SUD and MDD operated synergistically, such that they both arose from the same inherent cause.
The Prosecution’s expert, Dr Saluja, argued that Roszaidi’s SUD arose prior to and independently from his MDD, as his history of substance abuse began long before he started exhibiting symptoms of MDD. Hence, Roszaidi’s SUD should not be regarded as arising from an inherent cause. In contrast, the Defence’s expert, Dr Rajesh, contended that Roszaidi’s escalating drug abuse flowed from his MDD. Roszaidi’s SUD was a result of his MDD, which led him to become reliant on drugs as a coping mechanism. Therefore, his SUD and MDD operated together in a synergistic manner to exacerbate his overall mental abnormality. Since Roszaidi’s MDD arose from an inherent cause and Roszaidi’s MDD and SUD were inextricably intertwined, Roszaidi’s SUD similarly arose from an inherent cause.
The Majority accepted Dr Rajesh’s assessment and rejected Dr Saluja’s claims. They noted that Dr Rajesh’s reports were all directed at addressing the limbs of the Nagaenthran test and were hence directly targeted at the legal questions in issue. Further, Dr Rajesh had supported his assessment using facts specific to Roszaidi’s case, namely his escalation in drug consumption following two bereavements in May 2015 that triggered his MDD. These facts supported Dr Rajesh’s Synergy Claim that Roszaidi’s MDD and SUD operated together, with his MDD exacerbating his SUD.
In comparison, Dr Saluja’s examination of Roszaidi was not conducted with the Nagaenthran test in mind. In addition, he failed to account for the interaction between Roszaidi’s MDD and SUD. His position that Roszaidi’s MDD did not affect his ability to resist drug seeking behaviour was contradicted by his own evidence that Roszaidi was drug-free for around a year and a half before he started consuming drugs again after the onset of his MDD (instead of just escalating at that time from an already existing level of consumption).
Thus, the Majority held that the HC erred in holding that the Second Limb was not satisfied. However, it stressed that its decision was satisfied by Roszaidi’s MDD and his SUD operating together. It left open the question of whether SUD per se may satisfy the Second Limb.
(2) The Third Limb
The Majority then assessed whether Roszaidi’s MDD and SUD collectively substantially impaired his mental responsibility. To do so, it addressed the following questions: (i) what precisely does a substantial impairment of mental responsibility require, in the specific context of re-sentencing for drug trafficking (under section 5(1) of the MDA) or drug importation (under section 7 of the MDA) under section 33B of the MDA; and (ii) had Roszaidi discharged his burden of proving a substantial impairment of mental responsibility in relation to his drug trafficking offence?
(i) Guiding principles for determining when there is a substantial impairment of mental responsibility in drug trafficking cases
The Majority noted the following principles. First, what an accused person must establish under section 33B of the MDA is a substantial impairment of his mental responsibility for his acts and omissions in relation to the offence. This does not require a total impairment of mental responsibility, nor does the impairment have to rise to the level of unsoundness of mind(3) or automatism.(4) While an accused person’s inability to exercise willpower to control his physical acts would certainly suffice to show substantial impairment, his difficulty in controlling his physical acts may also be sufficient, depending on the degree of difficulty involved. Further, as to the relationship between the abnormality of mind and the accused person’s acts and omissions, the accused person’s abnormality of mind need not be the sole cause of his offending. Instead, the question is whether the abnormality of mind “had an influence” on his commission of the relevant acts.
Second, in determining whether the accused’s mental responsibility was substantially impaired, it is also essential to have regard to the role of the accused person’s abnormalities of mind not only in relation to the specific acts constituting the offence with which the accused person is charged, but also in relation to the broader question of what led him to decide to carry out those acts constituting that offence. This is important so as not to artificially ignore the reality of what affected the accused person’s mental responsibility for his acts and omissions in relation to the offence. The CA specifically referred to the case of Ahmed Salim v Public Prosecutor  SGCA 6 (“Ahmed Salim”). In that case, the CA drew a distinction between the accused person’s execution of a murder and their prior decision to commit the murder. It was held that even when the accused person executed a murder in accordance with a premeditated plan, the defence of diminished responsibility may be made out if he can prove that his mental disorder “substantially impaired his ability to make rational decisions and caused him to decide to kill the victim”. This would make the prior decision to kill “the product of a disordered mind, which is not functioning rationally”.
Third, the CA noted that under section 33B of the MDA, Parliament had enacted a special sentencing regime for the class of drug offenders who satisfy the requirements stipulated therein intending for the courts’ approach to be informed by the law on diminished responsibility as a partial defence to murder. However, although the concept of diminished responsibility operates in a functionally similar way both in the context of section 33B of the MDA and as a partial defence to murder under Exception 7 to section 300 of the Penal Code 1871, there will be a subtle difference of emphasis in its application in these two different contexts, stemming from the nature of the relevant offences.
Specifically, whereas many culpable homicides may take place in the heat of the moment, drug trafficking and importation offences under sections 5(1) and 7 of the MDA will almost invariably require some degree of planning and premeditation. Thus, in the context of drug trafficking offences, the court must pay particular attention to what influenced the accused person’s decision to commit the offence, and whether this decision was itself a product of the accused person’s decision-making faculties being substantially impaired, instead of focussing solely on the execution of the offence. This may be especially important where the underlying abnormality of mind is of such a nature as to distort the accused person’s ability to make decisions, as would be the case with disorders like SUD, which may make the acquisition of drugs for consumption his overriding preoccupation and the central focus of his life. Having regard to the particular nature of the impairments caused by these kinds of disorders, such a decision would be correctly characterised as “the product of a disordered mind”.
Fourth, there are at least three specific aspects of mental responsibility that are typically relevant under the Third Limb of the Nagaenthran test : (a) the accused person’s capacity to perceive his acts or omissions and know their nature (“basic cognitive ability”); (b) his capacity to know and appreciate whether those acts or omissions are wrong, in the sense of being both contrary to the ordinary standards of reasonable and honest persons and contrary to law (“moral and legal cognition”); and (c) his ability to exercise his will to control his actions such that he acts in accordance with what he knows to be right or wrong (“control”).
Having these aspects of mental responsibility in mind, the Majority further noted that rationality may be relevant to assessing both the second and third aspects of mental responsibility. However, it was unhelpful to introduce rationality as a label or touchstone to guide the overall analysis of impairment. Regarding the second aspect (moral and legal cognition), the specific inquiry was whether the accused person was able to distinguish right from wrong on an objective (or rational) basis, rather than on a subjective (and likely irrational) basis. The relevance of rationality to the third aspect of mental responsibility (control) is also not straightforward. If the accused person’s decision to commit the offence was in truth “the product of a disordered mind” which was not functioning rationally in the first place, his seeming rationality while following through with that earlier decision – in the sense that he may know what he is doing, and to that extent can be said to be carrying out seemingly conscious and deliberate actions – will not necessarily displace the availability of section 33B(3)(b) of the MDA.
Finally, whether the Third Limb of the Nagaenthran test was satisfied is primarily a question of fact for the court to decide (as opposed to the Second Limb of the test, which would primarily be a matter left for experts to determine).
(ii) Had Roszaidi satisfied his burden of proof?
There was no dispute that Roszaidi had basic cognitive ability and moral and legal cognition, in the sense that he knew what he was doing and that it was wrong and contrary to the law. The sole issue in respect of the Third Limb pertained to the third aspect, i.e., control. Based on the above principles, the CA held that the central question was whether Roszaidi’s abnormalities of mind had a real and material (as opposed to trivial or minimal) effect or influence on his ability to exercise control over his actions, and specifically to act in accordance with what he knew to be right. Moreover, it was also necessary to consider whether Roszaidi’s mental responsibility for both his specific act of giving the Drugs to his wife and his prior decision to traffic the Drugs were substantially impaired by his MDD and SUD.
Roszaidi submitted that his MDD and SUD substantially impaired his mental responsibility for deciding to commit the offence, as they undermined his ability to resist drug-taking and compelled him to continue trafficking drugs to feed his own addiction. Further, he asserted that his rational judgment was impaired by these conditions during the commission of the offence itself, as evidenced by: (a) his panic, fear and confusion at the material time; (b) his irrational decision to implicate his wife by passing the Drugs to her; and (c) the fact that he was under the influence of drugs at the time of the offence, which would have exacerbated his impaired judgment.
The Majority agreed with Roszaidi’s submissions. The Majority found that Roszaidi’s mental responsibility for his decision to traffic drugs was substantially impaired by his MDD and SUD. His MDD undermined his ability to work and to support the drug habit that he had had over the course of most of his life. This subsequently led him to turn to other sources of supply, in particular by trafficking in drugs for Is Cangeh, as he was paid in kind and would also steal from the drug consignments for his own consumption. His MDD also aggravated his SUD, which in turn drove him to prioritise securing a supply of drugs to feed his addiction as his overriding preoccupation.
In addition, the Majority found that Roszaidi’s specific act of giving the Drugs to his wife was directly and substantially impaired by his abnormalities of mind. The Majority concluded that the more plausible and compelling characterisation of Roszaidi’s act of giving the Drugs to his wife was that he acted impulsively and irrationally in a moment of panic, thereby demonstrating the impairment of his decision-making rather than evincing any such decision-making process itself. Roszaidi’s MDD may have caused him to be paranoid about being harmed by Is Cangeh if he threw away the Drugs. He likely overestimated the dangers of throwing away the drugs even though Is Cangeh had not made such threats and it was unclear whether Is Cangeh was part of a gang in the period leading up the offence. This paranoia was likely what caused Roszaidi to decide to pass the drugs to his innocent wife (who was heavily pregnant at that time), which did not appear to be the act of someone able, without substantial impairment, to exercise control over his actions.
Furthermore, the Majority found that the impairment of Roszaidi’s decision-making abilities was likely exacerbated by his consumption of copious amounts of drugs prior to the trafficking owing to his MDD and SUD. The influence of these drugs likely further heightened his feelings of fear and panic at the time of the offence. As such, the Majority held that Roszaidi’s MDD and SUD had substantially impaired his ability to exercise control over his acts in relation to the specific act of trafficking.
B. The Minority Judgment
(1) The Second Limb
The Minority first laid down its own guiding principles on assessing the utility of expert evidence regarding the aetiology (i.e. medical cause) of the accused’s mental disorders. First, it noted that a person’s mental state should be viewed holistically as an organic whole, rather than in “slices”. Second, where the expert evidence was prepared closer in time to the commission of the offence and where the expert had assessed the offender through a face-to-face interview, this would likely make the assessment more accurate as the accused would likely be more candid with his responses. Third, a mere assertion of general propositions without reference to the specific facts as well as context was unhelpful.
Having these principles in mind, the Minority considered Dr Saluja’s first report as the crucial piece of expert evidence. The Minority was of the view that the Majority’s rejection of Dr Saluja’s evidence – on the ground that it was not specifically directed at the Nagaenthran test – meant that it was analysing Roszaidi’s mental state in slices, instead of as an organic whole. Instead, any indications of diminished responsibility when Dr Saluja interviewed Roszaidi in 2015 should have been considered, to gain a more complete picture of Roszaidi’s mental state near the time of the offence. Further, Dr Saluja had interviewed Roszaidi personally just one month after the offence in the preparation of his first report, while Dr Rajesh’s first report was not based on any face-to-face session with Roszaidi and was also prepared more than four years after Roszaidi had been charged for the relevant offences.
The Minority further held that whilst Dr Rajesh’s general proposition that Roszaidi’s SUD and MDD might act in a synergistic manner was attractive in theory, it had to have an evidential basis to succeed. To substantiate this claim, Roszaidi had to provide evidence to establish a causal link between his MDD and his alleged escalated drug dependence (the “Causal Link”). This was because drug addicts experienced a natural escalation of consumption as they developed tolerance. Escalation of drug dependence per se did not advance the Synergy Claim. Instead, Roszaidi had to provide evidence as to the degree of his drug dependence escalation (i.e. whether his drug dependence escalated by a degree beyond the natural pattern of escalation typically observed in drug addicts) after the onset of his MDD to establish the Causal Link. However, Roszaidi did not produce such evidence to prove the Causal Link. Accordingly, the Minority rejected the Synergy Claim. Like the Majority, the Minority left open the question of whether Roszaidi’s SUD per se could be said to have arisen from an inherent cause and proceeded on the basis that only Roszaidi’s MDD arose from an inherent cause.
(2) The Third Limb
Having rejected the Synergy Claim, the Minority disagreed that Roszaidi’s mental responsibility was sufficiently impaired, since Roszaidi’s case that his mental responsibility was substantially impaired was largely premised on the Synergy Claim. The Minority further held that Roszaidi would have failed in establishing the Third Limb even if the Synergy Claim had been accepted.
The Minority first set out a few observations as to the application of the Third Limb. In the Minority’s view, Parliament had intended section 33B to operate in a measured and narrowly defined way, so as not to undermine the strict penalty regime in the MDA. Hence, the application of the exception to the death penalty under section 33B(3)(b) had to be tightly controlled, which extended to the application of the Third Limb as well. Further, in contrast with the Majority’s views, the Minority placed a greater emphasis on the importance of rationality, stating that rationality and control were inextricably linked. If an accused person’s conduct demonstrated rationality, the stronger inference was that the accused did not, as opposed to could not, resist his impulses.
Lastly, the Minority also opined that in addition to the narrow operation of section 33B of the MDA and the close link between rationality and control, it would be quite difficult to establish the defence under section 33B(3)(b) of the MDA due to the nature of the offence of drug trafficking. Drug trafficking offences would usually involve a series of acts that had to be committed across a span of time, as opposed to murder, where the acts constituting the offence would usually happen in a short span of time (and hence could more likely be characterised as occurring in the heat of the moment). In particular, where the accused’s conduct (in the trafficking of drugs) demonstrated organisation and/or evasion and/or opportunism, this would be the very antithesis of a lack of control. Hence, while there was no need to show total incapability to control one’s actions to satisfy section 33B(3)(b) of the MDA, an accused would have to manifest highly unusual symptoms and/or conduct and prove that he or she was truly hindered in making rational judgments and decisions to rely on this exception.
Based on the above observations, the Minority disagreed with the Majority’s assessment of the facts in relation to Roszaidi’s decision to the traffic the Drugs and his execution of the trafficking itself. In particular, the Minority found that Roszaidi did not adduce enough evidence to prove that his mental disorders impaired his impulse control and/or rational judgment to a sufficient extent to substantially impair his mental responsibility on either front.
The Minority first considered the nature of Roszaidi’s SUD and MDD. The Minority found that Roszaidi appeared to have a life outside of drugs, as he was able to maintain familial relationships and engage in social activities that did not involve drugs. Him quitting from his job was also of his own volition, and there was no evidence that he was incapable of working due to his disorders. Further, the Minority considered that while the experts suggested that drugs helped Roszaidi to cope with some depressive symptoms, whether his MDD led to an actual escalation in his level of drug consumption would have depended on factors including, in large part, the severity of his MDD. However, Dr Rajesh’s evidence on his MDD was brief, and his observations were made some four years after Roszaidi’s arrest, which could hardly represent his state of mind at the time of the offence. In the circumstances, the Minority was unable to find sufficient evidence showing that Roszaidi’s MDD was severe. Additionally, the Minority found that there was insufficient evidence as to the degree to which Roszaidi’s depression exacerbated his craving for drugs. Thus, the Minority found that Roszaidi did not prove that his MDD aggravated his SUD to a degree sufficient to satisfy section 33B(3)(b).
Next, the Minority evaluated Roszaidi’s evidence as to why he began delivering drugs for Is Cangeh. The Minority stressed that the analysis under the Third Limb should be focused on the accused’s state of mind at the time of the offence. In Roszaidi’s case, the act constituting the offence of trafficking was the transfer of the Drugs to his wife, which appeared to have been motivated by self-preservation as opposed to his impaired impulse control.
Further, the Minority held that even considering the broader question of why Roszaidi found himself in the situation in which he trafficked in the Drugs (i.e. why Roszaidi decided to start delivering drug for Is Cangeh, which later led to him trafficking the Drugs), he failed to establish the nexus between his trafficking of the Drugs and his alleged impaired impulse control in relation to his drug consumption. The Minority found that Roszaidi’s decision to traffic drugs was primarily motivated by the prospect of obtaining monetary remuneration after quitting his job, as evinced from statements taken from him in 2015. He was also motivated by the fear of reprisal from Is Cangeh for disobeying orders to deliver the Drugs in agreeing to follow through with the job despite his anxiety over the quantity of the consignment.
Finally, the Minority scrutinised the circumstances surrounding the offence and held that Roszaidi’s ability to resist the impulse to consume drugs was not weakened to such an extent that his mental responsibility was substantially impaired. The Minority held that the circumstances suggested that Roszaidi trafficked the Drugs to his wife with intentionality to achieve the calculated end of self-preservation. Roszaidi was rational to recognise that the consequences would differ depending on the weight of the drugs trafficked (and that he was trafficking a large amount of drugs). Hence, he wanted to complete the job quickly and devised an alternative plan to offload the Drugs to his wife. The Minority accepted the possibility that Roszaidi “thought (passing the Drugs to his wife) was safer than [him] carrying the drugs and driving around Singapore”. The Minority also opined that at the very minimum, Roszaidi had moments of rationality and self-control during which he could have resiled from the intention or plan to deliver the Drugs. This was indicated by his deliberate action and reasoned decision to pass the Drugs to his wife as he realised he was being pursued by the police, instead of insisting on executing the initial plan that night in the manner instructed by Is Cangeh.
IV. Lessons Learnt
Roszaidi Bin Osman v PP is a decision that is significant in two ways. Firstly, it affirms the central role of the evidence of psychiatric experts in determining the applicability of section 33B(3)(b) of the MDA, specifically the Second Limb of the Nagaenthran test. The court, however, will rigorously examine the reliability of expert evidence, placing heavy emphasis on how effectively it addresses the specific facts of the case and the different elements of the relevant legal tests involved.
Secondly, the decision affirms and builds on preceding landmark decisions such as Ahmed Salim. This decision emphasises that even if the accused person’s execution of an act in relation to their offence appears to be rational, the accused may still be able to contend that his responsibility for the offence was substantially impaired by an abnormality of mind. This is provided that he can show that his decision to commit the offence was in the fact the product of a disordered mind, in accordance with the principles laid out in this decision.
Written by: Isabelle Lim Yu Jie, 3rd-Year LLB student, Singapore Management University Yong Pung How School of Law.
Edited by: Ong Ee Ing (Senior Lecturer), Singapore Management University Yong Pung How School of Law.
 Being a courier under section 33B(3)(a) of the MDA means the offender’s involvement in the offence of drug trafficking is restricted to (i) transporting, sending or delivering the drugs or (ii) offering to transport, send or deliver the drugs or (iii) doing or offering to do any act preparatory to or for the purpose of his or her transporting, sending or delivering the drugs or (iv) to any combination of the activities mentioned in (i) – (iii).
 To understand why there was a dispute about whether Roszaidi’s SUD arose from an inherent cause, one may consider the case of PP v Jeffrey Phua  SGHC 73. The case explained the importance of establishing that the offender’s mental abnormality arose from an inherent cause for the defence of diminished responsibility. As a matter of policy, an offender who induces a mental abnormality in himself through external stimulants (e.g. by intentionally consuming drugs and alcohol) to give himself false courage to commit crimes should not be able to rely on his mental abnormality as a defence. The “inherent cause” requirement thus serves as a gatekeeping mechanism to ensure only mental abnormalities that arise internally that are beyond the offender’s control can be relied on for the defence. However, while substance abuse before a crime would not in general constitute an “inherent cause”, where the substance abuse was correlated with another condition arising from an “inherent cause” that the offender was also suffering from (such as MDD), substance abuse could be classified as an abnormality of mind arising from an “inherent cause” as well.
 See section 84 of the Penal Code 1871 (2020 Rev Ed). When an offender is of unsound mind, this means he is suffering from a mental abnormality that renders him either (a) completely incapable of knowing the nature of his actions or (b) completely incapable of knowing that what he is doing is wrong (whether wrong by the ordinary standards of reasonable and honest persons or wrong as contrary to law); or (c) completely deprived of any power to control his actions.
 Automatism describes a phenomenon whereby a person is completely unable to consciously control his muscular or bodily movements. Automatism negates criminal responsibility as the offence cannot be attributed to a voluntary act of the accused.