Case Details
- Citation: [2025] SGCA 8
- Title: Azuin bin Mohd Tap v Public Prosecutor
- Court: Court of Appeal of the Republic of Singapore
- Date: 27 February 2025
- Court/Proceeding No: Court of Appeal / Criminal Motion No 48 of 2024
- Judges: Sundaresh Menon CJ, Tay Yong Kwang JCA and Steven Chong JCA
- Applicant: Azuin bin Mohd Tap
- Respondent: Public Prosecutor
- Decision Type: Ex tempore judgment
- Legal Areas: Criminal Procedure and Sentencing — Appeal; Criminal Procedure and Sentencing — Appeal (adducing fresh evidence)
- Issue Focus: Whether fresh expert evidence is relevant/material to an appeal; abuse of process via “expert shopping”
- Statutes Referenced: Misuse of Drugs Act (Cap 185, 2008 Rev Ed) (“MDA”)
- Key Provisions: s 33B(1) and s 33B(3) of the MDA
- Related Lower Court Case: Public Prosecutor v Hashim bin Ismail and others [2023] SGHC 165 (“GD”)
- Judgment Length: 18 pages, 5,155 words
- Cases Cited (as provided): [2021] SGCA 18; [2023] SGHC 165; [2025] SGCA 8
Summary
In Azuin bin Mohd Tap v Public Prosecutor ([2025] SGCA 8), the Court of Appeal dismissed a criminal motion seeking leave to adduce further evidence on appeal. The applicant, convicted on a capital charge of drug trafficking and sentenced to the mandatory death penalty, sought to reopen his case on the defence of diminished responsibility under the Misuse of Drugs Act (MDA). After the trial judge rejected his diminished responsibility argument, he attempted to support his appeal with two new psychiatric and neuropsychological reports from different experts.
The Court of Appeal held that the proposed expert evidence was not material to the appeal. Although the court reiterated the framework for admitting further evidence on appeal (derived from Ladd v Marshall), it emphasised that, in criminal matters, the “non-availability” requirement is applied less rigidly, but the evidence must still satisfy the core requirements of materiality and reliability. Here, the new reports accepted that at least one essential limb of diminished responsibility was not made out, meaning the evidence could not likely influence the outcome.
Beyond the materiality point, the court expressed a broader concern that the applicant’s conduct amounted to “expert shopping”. The court cautioned that using successive expert reports to generate new or inconsistent lines of argument after an adverse decision risks abuse of process, even in the high-stakes context of criminal appeals.
What Were the Facts of This Case?
The applicant, Azuin bin Mohd Tap, was convicted by a High Court judge of a capital charge of drug trafficking and sentenced to the mandatory death penalty. The conviction arose under the MDA framework governing drug trafficking offences and the limited sentencing regimes that may displace the mandatory death penalty. The applicant did not dispute the charge at trial; instead, his defence strategy focused on whether he could bring himself within an alternative sentencing regime under s 33B(1) of the MDA.
Under s 33B(1), an accused person may avoid the mandatory death penalty if the court is satisfied that the accused suffers from diminished responsibility, subject to the statutory conditions in s 33B(3). In this case, it was not disputed that the applicant’s involvement was limited to that of a courier. However, the Public Prosecutor did not issue a certificate of substantive assistance. As a result, the trial judge treated the diminished responsibility question as the sole live issue relevant to sentencing.
At trial, the diminished responsibility defence turned on expert psychiatric evidence. The applicant relied on a defence expert, Dr Julia Lam, while the Prosecution relied on Dr Kenneth Koh. Both experts agreed that the applicant suffered from opioid use disorder and stimulant use disorder. Their disagreement concerned whether the applicant also suffered from persistent depressive disorder at the material time. The applicant’s case was that the combination of persistent depressive disorder, opioid use disorder, and stimulant use disorder substantially impaired his mental responsibility for the offence.
The trial judge rejected the defence. The judge preferred Dr Koh’s evidence over Dr Lam’s, largely because the judge disbelieved the factual account given to Dr Lam by the applicant and his sister. The judge found that the applicant and his sister had provided conflicting accounts to different experts—reporting chronic depression and adverse life circumstances to Dr Lam, but earlier telling Dr Koh that “everything was ok” and that the applicant’s behaviour was essentially normal. The judge concluded that only one of the accounts could be true and placed no weight on Dr Lam’s evidence. The judge found that the applicant did not suffer from persistent depressive disorder at the relevant time. For completeness, the judge also held that even if persistent depressive disorder were established, there was no evidence linking it to the applicant’s decision to traffic drugs; the applicant’s own evidence suggested he participated because it was lucrative and he could evaluate risk and reward.
What Were the Key Legal Issues?
The immediate legal issue before the Court of Appeal was procedural: whether the applicant should be granted leave to adduce further evidence on appeal. In Singapore, applications to admit further evidence are governed by the principles in Ladd v Marshall, which require that the evidence (i) could not have been obtained with reasonable diligence for use at the lower court, (ii) is material in the sense that it would probably have an important influence on the result, and (iii) is reliable.
However, the court also had to consider how these conditions operate in criminal appeals. The Court of Appeal has previously held that the “non-availability” condition is less paramount in criminal matters brought by an accused person, though it is not dispensed with entirely. The court therefore had to decide whether the applicant’s new expert reports met the materiality and reliability requirements, and whether the non-availability requirement could be assessed holistically in light of those other requirements.
A second, broader issue concerned abuse of process. The court noted that the applicant’s attempt to adduce fresh expert evidence appeared to be part of a pattern of “expert shopping”—seeking different experts to generate reports that could support new or inconsistent arguments on appeal after the trial judge’s findings. The court had to decide whether such conduct undermined the integrity of the appellate process, even where the stakes are high.
How Did the Court Analyse the Issues?
The Court of Appeal began by restating the established framework for admitting further evidence on appeal. It referred to the three Ladd v Marshall conditions: non-availability, materiality, and reliability. It also cited Singapore authority confirming that these conditions are not applied with full rigour in criminal cases brought by an accused person, because the court recognises the particular context of criminal proceedings and the need to ensure fairness. The court relied on its own earlier decisions, including Soh Meiyun v Public Prosecutor and Dzulkarnain bin Khamis v Public Prosecutor, for the general approach, and then explained the attenuated treatment of non-availability in criminal matters as clarified in Miya Manik v Public Prosecutor and another matter.
Despite the attenuated approach to non-availability, the Court of Appeal emphasised that the applicant still faced an “insurmountable difficulty” on materiality. The court’s reasoning was anchored in the statutory structure of diminished responsibility under s 33B(1) read with s 33B(3) of the MDA. At trial, the applicant’s diminished responsibility defence depended on satisfying multiple limbs: an abnormality of mind, causation by one of the specified aetiologies, and substantial impairment of mental responsibility. The Court of Appeal observed that the new expert reports did not overcome the trial judge’s essential findings.
In particular, the first new report was a psychiatric report by Dr Jacob Rajesh. Dr Rajesh opined that the applicant suffered from an abnormality of mind in the form of moderate opioid use disorder, and that this substantially impaired the applicant’s mental responsibility by causing preoccupation with procuring drugs to feed his addiction. However, Dr Rajesh acknowledged a critical deficiency: the applicant’s opioid use disorder did not arise from one of the three recognised aetiologies under s 33B(3)(b). This concession was decisive for materiality. If the statutory aetiology limb was not made out, the diminished responsibility regime could not apply, regardless of whether mental responsibility was otherwise described as impaired.
The second new report was a neuropsychological assessment by Ms Low Yung Ling. Ms Low’s report suggested that while the applicant had generally low intelligence, he did not meet criteria for any intellectual disability or disorder. While this might have been relevant to certain aspects of the diminished responsibility framework (for example, where arrested or retarded development of mind is alleged), it did not supply the missing statutory element identified by the trial judge and accepted as absent by the new psychiatric report. In other words, the new evidence did not create a plausible pathway to satisfy the statutory requirements for diminished responsibility.
The Court of Appeal therefore concluded that the proposed expert evidence was not material because it accepted that at least one essential limb of diminished responsibility was not made out. The court reasoned that evidence which cannot influence the result—because it does not address the statutory requirements in a way that could change the outcome—fails the materiality condition. The court’s approach reflects a practical appellate logic: fresh evidence is not admitted merely to generate new factual disputes or alternative narratives; it must be capable of affecting the legal outcome under the governing statutory test.
Finally, the court addressed a more general concern about the applicant’s conduct. It noted that the applicant appeared to be engaging in “expert shopping” to lay the groundwork for running new and even inconsistent lines of argument on appeal. The court referred to prior cautions against abuse of process in criminal proceedings, including Miya Manik, and took the opportunity to clarify that expert shopping of the kind seen in this case falls squarely within conduct amounting to abuse of process.
Although the court’s primary reason for dismissal was immateriality, its additional observations serve as a warning to litigants and counsel. Where a trial judge has already assessed conflicting expert evidence and made findings—particularly findings grounded in credibility and factual accounts—an accused should not assume that successive expert reports will automatically be treated as admissible “fresh evidence” on appeal. The appellate process is not meant to be a forum for iterative expert selection designed to circumvent adverse findings.
What Was the Outcome?
The Court of Appeal dismissed the applicant’s criminal motion for leave to adduce further evidence. The court held that the two new expert reports were not material to the appeal because they did not address the statutory requirements for diminished responsibility in a way that could likely influence the outcome.
In addition to dismissing the motion, the court expressly cautioned against “expert shopping” and indicated that such conduct may amount to an abuse of process. The practical effect is that the applicant’s appeal could not be supported by these new reports, and the trial judge’s rejection of diminished responsibility remained undisturbed.
Why Does This Case Matter?
This decision is significant for practitioners because it clarifies how the Court of Appeal will apply the Ladd v Marshall framework to fresh expert evidence in criminal appeals, particularly in diminished responsibility cases under the MDA. While the court recognises that non-availability is less paramount for accused persons, it does not relax the materiality requirement. Fresh evidence must be capable of changing the legal outcome under the statutory test; evidence that concedes a missing statutory limb will almost certainly be rejected.
For lawyers preparing appeals, the case underscores the importance of aligning expert evidence with the precise statutory elements. In diminished responsibility litigation, it is not enough for an expert to describe impairment or abnormality of mind in general terms. The evidence must engage with the specific aetiology requirements in s 33B(3)(b) and the causal link to substantial impairment. If the new evidence cannot satisfy those elements, it will fail the materiality threshold even if it is otherwise reliable.
Second, the court’s discussion of “expert shopping” provides a procedural integrity lens. The court’s willingness to characterise expert selection tactics as abuse of process signals that appellate courts will scrutinise not only the content of fresh evidence but also the manner in which it is obtained and deployed. Counsel should therefore consider strategic discipline: where a trial judge has rejected an expert account based on credibility and factual inconsistency, an appeal should be grounded in legitimate appellate review, not in attempts to repackage the case through successive expert reports that do not genuinely address the missing legal elements.
Legislation Referenced
- Misuse of Drugs Act (Cap 185, 2008 Rev Ed) — s 33B(1) and s 33B(3)
Cases Cited
- Ladd v Marshall [1954] 1 WLR 1489
- Soh Meiyun v Public Prosecutor [2014] 3 SLR 299
- Dzulkarnain bin Khamis v Public Prosecutor and another appeal and another matter [2023] 1 SLR 1398
- AnAn Group (Singapore) Pte Ltd v VTB Bank (Public Joint Stock Co) [2019] 2 SLR 341
- Public Prosecutor v Mohd Ariffan bin Mohd Hassan [2018] 1 SLR 544
- Miya Manik v Public Prosecutor and another matter [2021] 2 SLR 1169
- Nagaenthran a/l K Dharmalingam v Public Prosecutor and another appeal [2019] 2 SLR 216
- Public Prosecutor v Hashim bin Ismail and others [2023] SGHC 165
Source Documents
This article analyses [2025] SGCA 8 for legal research and educational purposes. It does not constitute legal advice. Readers should consult the full judgment for the Court's complete reasoning.