Lai Wei Kang Louis

Torn Fealty to the Courts and Science: Conundrums over Medical Expert Opinions (II/II)

By Agnes Lo, Bryont Chin, Darren Ang, Leon Tay & Louis Lai

The previous section of this article examined the different considerations that affect the weight accorded to expert evidence.1 It was observed that judges scrutinize the expert himself (his qualifications and the level and relevance of his specialization) and also his testimony (its cogency, internal consistency, and consistency with the facts).

A survey of local case law and overseas publications reveals issues surrounding this assessment. These have been directed to the reliability of expert opinions itself, applying generally to all experts. Unfortunately, local jurisprudence has not addressed these concerns.

The lacuna in local jurisprudence on this point is especially unfortunate given the widespread prevalence of and reliance upon medical expert opinion in Singapore. It is thus pertinent to examine these issues and their causes in detail.


A. Partiality and bias of experts

Case law reflects a persistent concern about the partiality and bias of experts but also a recognition that this will persist as long as litigation remains adversarial. Ideally, under Order 40A Rule 2(2) of the Rules of Court2 [ROC], experts should bear an exclusive duty to the Court; however, this is usually not the case in practice. A “market-place” mentality continues to prevail, in which parties select experts because the latter’s views are “already known and, consequently, would advance the party’s case.”3 Both the courts and commentators like Professor Pinsler have acknowledged that the source of this paradigm is the adversarial model, since parties assume that their “remuneration of the expert justifies a measure of loyalty that will somehow manifest to his advantage in the determination of the case before or at trial”.4 Therefore, as long as the adversarial model continues to be adopted, parties will continue to pay, retain, and offer the experts future engagements—all of which incentivise experts to provide opinion evidence slanted in favour of the clients who engage them.5

To make matters worse, breaches of the procedural duty under Order 40A above attract no direct penalties in themselves. There is only an evidential penalty: if an expert is found to be partial, the court completely or partially disregards his testimony.6 This does not seem to have been enough: from the introduction of Order 40A in 2000 to date, the courts have continued to observe bias in experts.7 Therefore, bias among experts remains a real problem in the court today.

B. A fear of testifying in Court

Also flowing from the adversarial model and the process of adjudication itself is medical experts’ intrinsic fear of testifying in court. Experts—and medical experts in particular—tend to steer clear of the witness stand for two reasons: a fear that they may not be sufficiently competent to testify, and a fear that they may be shamed or wronged on the stand.8

While there is no equally comprehensive study, local doctors have expressed the same fears of testifying due to natural embarrassment and a fear of damaging their colleagues’ reputations.9 Failing to address these fears will restrict plaintiffs’ access to medical experts or otherwise make engaging experts more expensive. This reluctance will affect the quality and accessibility of court adjudication, reliant as it is on expert testimony.

C. Insufficiency of factual bases for medical opinions

Experts often have insufficient facts to support their opinion. This is because in litigation, they are likely to be engaged before trials begin since their opinions are critical in establishing the client’s case and thus predict the likelihood of success at trial.10 However, this means that much of the evidence the expert relies upon to develop his report and testimony will be “untested raw material” since this evidence has yet to be tested in court.11 This concern came to a head in Khoo Bee Kiong,12 where the court expressly questioned the factual basis of an expert opinion prepared with affidavits of evidence in chief.

This is likely to be aggravated in medical negligence claims, where the recent Supreme Court Practice Directions13 impose an accelerated case management timeline. As an expert report must now be filed before the claim itself begins, medical experts have less time and evidence to formulate their opinions.


Apart from issues with the expert opinions themselves, there are also notable concerns with the judicial treatment of medical expert opinions reflected in empirical studies. These suggest that there are systemic issues with judges’ competence to assess the reliability and credibility of a medical expert’s opinion. These issues manifest themselves in two main ways: lack of clarity and improper assessment of an expert opinion’s reliability and weight.

A. Lack of clarity

At its core, the court’s assessment of the weight to be given to a medical expert’s opinion is a discretionary exercise. It is naturally opaque and applied circumstantially, and may hence appear uncertain. This means that the other stakeholders involved—lawyers, clients, and the medical experts themselves—may misunderstand the standard expected of them. Jurs, for instance, observes that legal professionals tend to over-estimate the value of personality and credentials, whereas judges place a greater emphasis on partiality and bias, tentativeness, and the technicality of the opinions proffered.14 Clarity in this area is much needed;15 consensus and better articulation of the relevant considerations would assist greatly.

B. Improper assessment of reliability and weight

Beyond a lack of clarity, too great an emphasis may also be placed by judges on considerations unrelated to or insignificant in assessing the weight of opinion evidence. For instance, “impressions of the analyst’s demeanour and credibility, like the ability to survive cross-examination, will not in most cases provide rational means of assessing the probative value of an opinion.”16 The English courts, for example, have been criticised for assessing expert opinion evidence on this basis, which has led to factually unsustainable acquittals.17

Studies suggest that this improper assessment persists because medically-untrained judges and jurors may not be sufficiently competent to assess the value of medical expert opinions. For instance, jurors look for consensus supporting the expert opinion, whether the opinion is applicable in the case at hand,18 and how experts communicate their opinions,19 instead of instead of assessing the true admissibility and reliability of the expert opinion. These indicators do not, however, necessarily go towards the veracity of an opinion.20 Where earlier studies have suggested that that this may be due to a lack of education in the expert’s field,21 it is understandable why some doctors feel that laypersons like jurors “should not decide medical malpractice cases because of the arcane issues involved in the practice of medicine.”22

Local jurisprudence has only engaged these concerns in the abstract. Ronald Wong posits that the law’s insistence on the finality of an opinion for it to be accepted as evidence conflicts with the scientific method, which relies not on finality, but rather social acceptance to establish a theory as valid.23 This mirrors the observation in Levett and Korvera’s review that “individuals often are unable to evaluate statistics or methodology properly… [such that] it is reasonable to assume that jurors may be unsuccessful in independently detecting flaws in research presented by an expert in court.”24 Nonetheless, Wong has argued that it is still preferable for a judge to continue to adjudicate on the issue, and if the expert evidence is insufficiently reliable, a judge ought to make his findings of fact on the burden of proof.25 Wong’s argument—defended on grounds of a public interest in resolving disputes—contrasts with Professor Hor’s view that judges lack any institutional capacity to determine the veracity of expert opinion. 26

While the argument that professional judges ought to continue to adjudicate on expert opinions resounds with a strong motivation to do so, the question of institutional competence will inevitably haunt the ability of a judge to assess an expert’s opinion. This is especially the case if adjudication leads to reliance on wrong or inaccurate expert opinions as expressed in the studies above.


Concerns over unreliable expert opinions have been the subject of statutory reform. The government has astutely implemented a certification regime for opinion evidence for psychiatrists in criminal cases under s 270 of the Criminal Procedure Code27 [CPC] which has recently come into force this year. The amendments provide that that only certified psychiatrists can testify. This places the control over the admission and use of psychiatrists’ opinions in the hands of a Selection Committee instituted for these purposes.

In other aspects, however, reform continues to be lacking. The independence of experts continues to be secured by weak duties under s 269 CPC which do not depart from the phraseology of Order 40A ROC. The amendments to the CPC do not address the deeper concerns relating to adversarial litigation or pronounce on the feasibility of alternatives such as independent experts or assessors.

Therefore, the fundamental question remains as to whether the amendments will indeed improve the reliability of psychiatric evidence and be a viable option across other classes of medical experts as well; or, alternatively, whether it would entrench a preferred doctrine of psychiatric testimony.28 Psychiatrists have questioned why they were the only class of expert that required supervision, while the Criminal Bar expressed that it would be preferable if the selection process also included defence counsel as a member of the Selection Committee.29 If the latter is the case, then the amendments contribute to the issues of bias instead of resolving them.

Beyond partiality concerns, other issues raised above have yet to be verified and recognized. While the concern that experts may not have sufficient factual evidence to support their opinions has been expressed judicially, the expediting of court procedure is unhelpful in this respect. Issues that judges may lack the institutional capacity to assess medical expert opinions, or that they may demand a different standard from the general public, have not been validated in Singapore. While there are extra-legal methods employed to cope with these such as a training course for medical experts, the impact of these courses has not yet been observed.


The discussion above has traced a number of difficulties in the use of medical experts’ opinions, as well as the use of experts in general. The judicial approach to assessing the probative value and reliability of opinions is plagued with difficulties stemming from intractable concerns that medical experts tend to be partial towards the party that hired them, and that they often lack sufficient facts to properly develop an opinion. Although there are both existing procedural laws and extraneous support to safeguard the reliability of medical expert opinions, these are often watered down by parties’ adversarial mentalities. Where there is little incentive to cooperate, parties do not actively rely on the same measures such as concurrent expert evidence or discussion. Other issues, such as fear among medical professionals of proffering testimony against their fellow doctors, or the competence of the Court to adjudicate on the same, have hardly been the subject of discussion by the legal community in Singapore.

This is unfortunate as expert opinions are the lifeblood of many disputes. Even before the case commences, expert opinions are important in managing client expectations, where the expert’s assessment indicates the client’s likelihood of success.30 Medical experts are of special significance in the field given that they are relevant in many legal disputes and, in fact, comprise the bulk of experts sought.

Meeting the concerns above would require lawyers, courts, and medical experts alike to come to a clear consensus on their roles and competencies in adjudication. Coping with the difficulties of an adversarial model will also require a change in mindset and culture: lawyers and courts must emphasise to medical experts that in testifying, they are helping society as a whole. In this regard, the authors posit that empirical studies will be helpful in assessing the gravity of each issue, and the effectiveness of measures to cope with them.

*The authors are a group of undergraduate students in the National University of Singapore, and are presently in the course of an empirical research project on the subject.

[1] See Agnes Lo, Bryont Chin, Leon Tay & Louis Lai, “Torn Fealty to the Courts and Science: Conundrums over Medical Expert Opinions (I/II)”, online: Juris Illuminae, Vol 10 <>.

[2] Cap 322, R 5, 2014 Rev Ed Sing.

[3] Jeffrey Pinsler, “Expert Evidence and Adversarial Compromise: A reconsideration of the Expert’s Role and Proposals for Reform” [2015] 27 Sing Ac LJ 55 at [2].

[4] Ibid at [15].

[5] Vita Health Laboratories Pte Ltd v Pang Seng Meng [2004] 4 SLR 162, at [81].

[6] If the expert attempts or is seen to be an advocate for his party’s cause, he will inexorably lose credibility: per VK Rajah JA in Vita Health Laboratories Pte Ltd v Pang Seng Meng [2004] 4 SLR 162 at [83].

[7] Supra note 3 at [4].

[8] See e.g. “Medical Malpractice - Expert Testimony” (1965-1966) 60 Nw UL Rev 834.

[9] See Joseph Sheares, “Writing the Expert Report and Testifying in Court (Part 2)”, SMA News (February 2015), online: at 23.

[10] Amanda Stevens, “Editorial: Reliability and cogency of expert witness evidence in modern civil litigation” (2011) 66 Anaesthesia 764.

[11] Khoo Bee Keong v Ang Chun Hong [2005] SGHC 128 at [72].

[12] Ibid.

[13] See Sing, The Supreme Court Practice Directions (2017) part XXIII, s 158(1), referring to Appendix J (High Court Protocol for Medical Negligence Cases), online: <> at 4.1-4.2.

[14] Ibid.

[15] See e.g. the Ministry’s comments in proposing amendments to s 270 of the CPC, which it expressed to be for the purposes of ensuring that evidence given by psychiatrists is “competently arrived at and objective”: Siau Ming En, “Proposed psychiatric panel must be large enough for smoother defence: Lawyers”, Today (28 July 2017), online: <>.

[16] Gary Etmond, “Legal versus non-legal approaches to forensic science evidence” (2016) 20:1 IJEP 3 at 24.

[17] Ibid.

[18] Lora M Levett & Margaret Bull Korvera, “The Effectiveness of Opposing Expert Witnesses for Educating Jurors about Unreliable Expert Evidence” (2008) 32:4 Law and Human Behaviour 363-374, at 364.

[19] Andrew W Jurs, “Expert Prevalence, Persuasion, and Price: What Trial Participants Really Think About Experts” (2016) 91 Ind LJ 353.

[20] Kovera MB, McAuliff BD & Hebert KS, “Reasoning about Scientific Evidence: Effects of Juror Gender and Evidence Quality on Juror Decisions in a Hostile Work Environment case” (1999) 84:3 J Appl Psychol 362 at 365.

[21] See e.g. Kalven, Harry Jr & Hans Zeisel, The American Jury (Chicago: University of Chicago Press, 1966) at 153; cited in Sanja Kutnjak Ivkovic & Valerie P Hans, “Jurors’ Evaluations of Expert Testimony: Judging the Messenger and the Message” (Cornell Law Faculty Publications, Paper 385, 2003) at 443.

[22] Neil Vidmar, “Lay Decision-Makers in the Legal Process” in Peter Cane & Herbert M Kritzer, The Oxford Handbook of Empirical Legal Research (OUP, 2010) 626, at 633.

[23] Ronald JJ Wong, “Judging between Conflicting Expert Evidence” (2014) 26 Sing Ac LJ 169.

[24] Supra note 18.

[25] Supra note 23.

[26] Ibid, citing Michael Hor, “When Experts Disagree” (2000) Sing JLS 241 at 243.

[27] Cap 68, 2012 Rev Ed Sing.

[28]Supra note 15.

[29] Ibid.

[30] Supra note 10.

The PDF version of this article is available for download here.

Torn Fealty to the Courts and Science: Conundrums over Medical Expert Opinions (I/II)

By Agnes Lo, Bryont Chin, Leon Tay & Louis Lai


The Singapore courts are well-accustomed to hearing technically complex disputes, and disputes involving medical issues may present the most complex of these cases. Where judges and counsel are unable to divine the implications of facts and evidence at hand, they inevitably turn to expert witnesses. Expert witnesses assist in interpreting the facts, opining on what these facts mean, and provide specialized knowledge and information so very crucial for a judgment to be made.

Expert witnesses have become necessary ever since complexity in technical matters increased beyond a layman’s untrained capacity. It was understood that when the machines inevitably got involved in disputes, judges had to call on experts to advise them. However, judges do not blindly defer to the authority of the expert. Care is necessarily taken to differentiate between different opinions proffered by each expert, and not every testimony is given equal weight or admitted without any questions. A clear example where the judge departs from the views of an expert is in situations of bias. Another possible difficulty is in finding an objective approach to evaluate competing expert opinions. In such situations, whose opinion is to be preferred and given more weight? Is a professor’s academic opinion more reliable than that of an experienced practitioner lacking in qualifications? These questions continue to plague the courts today.

In a two-part series, this article sets out a preliminary examination of the main factors considered by the court in assessing the proper weight to be given to expert testimony. Medical experts are given foremost consideration as they feature prominently among the expert witnesses appearing before the courts. In a following article, we will also examine inconsistencies and incoherence in the courts’ use of expert evidence, and discuss recommendations for future use of expert evidence.

A. The use of medical experts in court

Medical expert opinions are widely admitted in criminal and civil trials. In criminal cases, these opinions are necessary to determine the psychological or physiological state of the accused persons, from which the judge can establish the legal elements of the offence. When deciding on sentencing, expert opinion also informs the judge of facts from which he can find exacerbating or mitigating factors. In civil matters, liability of the accused and damages to be awarded often depends heavily on the assessment of a medical expert. After all, judges are hardly able to decide what an appropriate sum for medical expenses should be, or how much income would have been lost as a result of an injury. Of course, medical expert opinions are most often adduced in physical injury cases,1 and when trespassing into the realm of medical expertise, judges are loath to substitute their own views for those of the proper experts in the field. In this regard, judges thus place a greater weight on the testimony of a defendant doctor’s own peers.

B. The present litmus tests for the admissibility and reliability of opinions of medical experts

Prior to the introduction of the adversarial criminal system in the 18th century, there was no legal procedure to define experts qua expert witnesses;2 experts would usually be summoned as jurors or witnesses. Evidentiary rules and objections were subsequently developed to standardise the types of evidence and how they can be presented before the court. While the rule against opinion being admissible as evidence emerged alongside the prohibitive rule against hearsay, experts’ opinions are an exception to this otherwise strict rule. This exception was necessary in the adversarial system for experts to provide opinions as witnesses without having observed the facts.

The present legal framework for the admission and giving weight to expert evidence bears two stages of analysis. Judges as finders of fact must contend with the question of whether the expert’s opinion is admissible as evidence, and if so, whether the expert’s opinion is of sufficient weight to be relied upon to establish a fact in issue. The former is governed largely by Section 47 of the Evidence Act and interpretive cases, while the latter is largely a matter expounded upon by case law.

Section 47 of the Evidence Act essentially requires counsel to establish three points to admit expert opinions as evidence:

(a) The pleaded point must be one of “scientific, technical or other specialised knowledge”.3 The ambit of such knowledge and whether a particular field would fall within it seems to be open to discussion, and local courts have yet to pronounce on the specific test. There have been suggestions for reference to tests in foreign jurisprudence, such as the more lenient test in Frye v United States4 (“Frye”); or a more stringent inquiry under Daubert v Merrell Dow Pharmaceuticals.5

(b) The individual giving the opinion must be an expert, who must have obtained the knowledge applied in his opinion “based on training, study or experience”.6 A judicial determination of whether this is made out is discretionary, and often turns on the qualifications, experience, and credibility of the expert in question.7

(c) In the round, the opinion provided must be “likely to assist” the Court in making its determination of fact. This is a lower threshold than that under the same provision before the 2012 Amendments to the Evidence Act.

Once admitted, the court generally gives weight to the expert opinion unless it is later found to be ”obviously lacking in defensibility”.8 In cases where only one expert opinion is adduced or where the experts are in agreement, there are few obstacles that may lead to the courts giving it less weight. This is contrasted to cases where competing expert opinions are adduced in court, where there is interest in how a judge chooses which view to adopt, especially so in the absence of legitimate technical experience. A brief survey of cases involving medical experts affirms a multi-factorial approach to be taken. Some of the factors are examined below.

1. Expert's qualifications and experiences

The most prominent factor is the expert’s qualifications. “Qualifications”, as explained by the Court of Appeal, refers not to an expert’s “professional titles” but instead refers more generally to the expert’s “knowledge and familiarity”.9 While it is generally true that actual experience lends more weight to an expert testimony than mere paper qualifications, the High Court has qualified this by stating in obiter that this was “not an inevitable rule of thumb”.10

The relevance of practical experience to the subject matter of the case is considered down to a micro-level: the court has differentiated between experts with clinical experience in cancer diagnosis and experts with clinical experience in cancer treatment,11 and between experts in the treatment of drug addicts and experts in recognizing signs of drug addiction.12

Other factors that affect the weight given to an expert testimony are his experience doing research relevant to the case at hand,13 and his experience practicing in the Singapore context.14 That a medical expert witness has experience treating one of the parties involved also lends authority to his testimony, since he would be more familiar with that party’s condition(s); however, his familiarity and personal relationship with the party raises clear possibilities of bias that must be dealt with.15

2. Impartiality of expert witness

The testimony of even the most qualified expert will not pass muster if it is tainted by bias. Hired guns fighting for the parties that called (and paid) them can hardly be relied on to provide accurate testimony. The influence of bias is great in practice due to monetary incentives being available, the priming of experts to be a part of the legal team, and the lack of safeguards against errant experts trying to manipulate facts to support a biased opinion.16

Although expert witnesses are appointed by parties themselves, their ultimate duty is always to the court.17 They cannot become mercenaries for hire, bending the facts for the highest bidder. Bias is especially dangerous for expert witnesses because, by definition, expert witnesses have expertise that the judge does not; an errant expert could easily mislead the judge and dictate the outcome. Therefore, judges must remain alive to the dangers of expert bias. Given the high stakes, judges impose only a low threshold for finding bias: even “perceived partiality or inclination” on the expert’s part can suffice to disqualify him for bias.18

3. Alignment with factual evidence

The words of even the most illustrious expert have no weight if it does not comport with the facts. Although disagreement in expert opinions is so common as to be almost inevitable, expert opinions must remain based on the facts established by the court. Expert testimonies that contradict the facts often prove fatal to that side’s case.19 When faced with insufficient evidence or evidence that contradicts the point their side wants to prove, it would be better for the experts to concede “where they ha[ve] to”20 than have the credibility of their entire report doubted by the court.

Factual evidence can also be used as a weapon to knock down opposing experts’ testimonies. In Hii Chii Kok v Ooi Peng Jin London Lucien and another,21 since the plaintiff’s expert could not provide “objective clinical data to support his assertions”, the court strongly preferred the defendant’s experts, whose testimonies “convincingly” countered the plaintiff’s expert’s testimony “point-by-point”.

Finally, expert testimonies should be precise and specific. Sweeping generalisations and conjecture are frowned upon, even more so when they are unsupported by evidence22 or outside the expert’s field of expertise.23

4. Internal consistency of testimony

Inconsistency in an expert’s testimony casts a long shadow over his credibility. The degree of internal consistency has been described as one of the “paramount” considerations that courts will consider when assessing such reports.24 Given that experts are meant to guide the court, admitting the evidence of a muddled and confused expert would be akin to the blind leading the blind. Therefore, courts readily reject inconsistent expert reports or grant them less weight. An example would be in Chua Thong Jiang Andrew v Yue Wai Mun and another25 where the expert’s quality was harshly criticized because of various self-contradictions in his oral testimony plus ambiguities and conflations in his expert report. The court issued a scathing dismissal of his report, describing it as an “illogical and unconvincing” explanation that was “completely off the mark”.

On the other hand, experts who can maintain a high degree of internal consistency in their testimony will enjoy high praise from the courts. In Public Prosecutor v Tengku Jonaris Badlishah bin Tengku Abdul Hamid Thani,26 the court described the prosecution’s expert in the most admiring terms, calling his opinion “consistent, impressive and able to stand up to objectivity”. It should be noted, however, that a dogmatic expert who refuses to change his view even in the face of overwhelming evidence to the contrary is not necessarily preferable to a reasonable expert who concedes in such situations. Experts need not defend their point to the death for fear of sounding inconsistent: courts understand and appreciate an expert changing his view to consider and account for shortcomings in his side’s case. In Khek Ching Ching v SBS Transit Ltd,27 the court noted that under “withering” cross-examination, the plaintiff’s expert had conceded that he was unable to confirm with complete certainty the causation of the plaintiff’s injury. Because he had continued to maintain his position while still conceded where he had to, the court commended him as a “generally good” expert witness that had testified “professionally”, and noted that he had been “of assistance to the court”.

5. Expert's methodology

Although courts are loath to put themselves into the expert’s shoes, an expert report derived using clearly flawed methodology will still be dismissed. It should be noted that an expert’s level of qualification is a separate and distinct factor from the quality of his methodology (although, hopefully, the former would lead to the latter). Ong Pang Siew v Public Prosecutor28 is the main case where this factor has been relevant. In that case, where the accused pleaded the defence of diminished responsibility, the court harshly criticized the prosecution witness for his poor investigative methodology29 when writing his report. The defence witness’ “undoubtedly more comprehensive” methodology meant that his report turned the tide, and led the court to allow the appeal.

6. Expert pushing his/her own case theory

While it is natural for experts to form case theories from prolonged exposure to a case, it is prudent for experts to remain objective in their testimonies and not venture into interpreting facts. Once experts accept the responsibility of testifying, they must resist this temptation and stay impartial to the facts. However, this is easier said than done.

In Eu Lim Hoklai v Public Prosecutor,30 the Court of Appeal explicitly pointed out the Prosecution witness’ “over-enthusiastic allegiance” to her own case theory, and how, in her “absolute certainty” that it was correct, she had overlooked its “inherent improbabilities” and “uncertainty in the evidence”.31 Although V K Rajah JA (as he then was) restrained himself to stating that her “reliability as an expert witness...may rightly be called into question”, the failure of the Prosecution’s “most important” witness in this important regard defeated the Prosecution’s case.32 Advocacy must be left to the lawyers, and the experts should keep within their own field.

C. Conclusion

As explained in the introduction, the exception of the expert witness was necessitated by the increasing complexity of legal disputes. In the years since, as the sight of experts in courtrooms became commonplace, rules in this area appeared and grew. Much of the law on the admissibility and weight of expert evidence was created by judges, since it is for them that the issue is most pressing. Judges rely on experts to guide them through their fields of expertise, to steer them through the pits of ignorance to reach justice, fairness, and truth. Thus, when searching for guides, judges are just like the rest of us: they look for persons with impartiality, experience, clarity, and intellectual honesty. Such paragons of virtue may be hard to find, but there is hardly an alternative. Trade-offs have to be made, and the second part of this series will examine them in greater depth.

[1] This has been established in a number of American studies. See Andrew W Jurs, “Expert Prevalence, Persuasion, and Price: What Trial Participants Really Think about Experts” (2016) 91 Ind LJ 353, which records that physicians make up the majority of experts at 37.5%; and Champagne et al, “An Empirical Examination of the Use of Expert Witnesses in American Courts” (1991) 31:4 Jurimetrics J 375, which observed that most experts were physicians (48%), and experts were mainly used in physical injury cases, and Samuel R Gross, “Don’t Try: Civil Jury Verdicts in a System Geared to Settlement” (1996) 44 UCLA L Rev 1, which observed that medical experts make up the majority of experts.

[2] Tal Golan, “The History of Scientific Expert Testimony in the English Courtroom” (1999) 12:1 Science in Context 7 at 9.

[3] Evidence Act (Cap 97, 2012 Rev Ed Sing, s 47(1).

[4] 293 F 1013 (DC Cir 1923).

[5] 509 US 579 (1993).

[6] Supra note 3 at s 47(2).

[7] Fok Chia Siong v Public Prosecutor [1999] SGCA 5 and Wong Swee Chin v PP [1981] 1 MLJ 212.

[8] Saeng-Un Udom v Public Prosecutor [2001] 2 SLR(R) 1; [2001] SGCA 38 at [26].

[9] Muhammad Jefrry v Public Prosecutor [1996] 2 SLR(R) 738; [1996] SGCA 44 [Jefrry] at [107].

[10] Sakthivel Punithavathi v Public Prosecutor [2007] 2 SLR(R) 983; [2007] SGHC 54 [Sakthivel Punithavathi] at [75].

[11] Noor Azlin Bte Abdul Rahman v Changi General Hospital Pte Ltd and others [2018] SGHC 35 (“Noor Azlin”) at [63].

[12] Jefrry, supra note 9 at [90]-[91].

[13] Supra note 11 at [23].

[14] Ibid at [63].

[15] Tan Teck Boon v Lee Gim Siong and others [2011] SGHC 76 at [7]; AOD, a minor suing by the litigation representative v AOE [2014] SGHCR 21 at [63].

[16] Jeffery D Pinsler, “Expert’s Duty to be truthful in light of the Rules of Court” (2004) 16 SAcLJ 407.

[17] Rules of Court (Cap 322, R 5, 2014 Rev Ed Sing), O 40A, r 2.

[18] Public Prosecutor v Thangaraju Sarukesi [2007] SGMC 7 at [71].

[19] See generally Sheila Leow Seu Moi v Public Prosecutor [2001] SGDC 376 [Sheila Leow]; Yeo Henry (executor and trustee of the estate of Ng Lay Hua, deceased) v Yeo Charles and others [2016] SGHC 220 at [63]-[67], [89], and [91]; Eu Lim Hoklai v Public Prosecutor [2011] 3 SLR 167; [2011] SGCA 16 [Eu Lim Hoklai] at [58], and Public Prosecutor v Tong Lai Chun [2003] SGMC 7 at [183].

[20] Khek Ching Ching v SBS Transit Ltd [2010] SGDC 220 at [95].

[21] [2016] SGHC 21.

[22] Sheila Leow, supra note 22 at [118]-[119].

[23] Eu Lim Hoklai, supra note 22 at [58].

[24] Sakthivel Punithavathi, supra note 10 at [75].

[25] [2015] SGHC 119.

[26] [1998] SGHC 401.

[27] [2010] SGDC 220.

[28] [2011] 1 SLR 606; [2010] SGCA 37.

[29] Firstly, the witness had failed to interview people who had recently contacted the accused person (thus breaching the diagnostic guidelines in the DSM-IV-TR, a reputed psychiatric manual). Secondly, he had also failed to investigate what the court considered to be relevant considerations, viz. the accused person’s changing jobs three times in the 18 months before committing the crime and his diabetes, which increased the risk of depression. Thirdly, he had interviewed the accused person in Mandarin even though he knew that the latter was more comfortable in Hokkien. The court thus condemned his methodology as an “unsatisfactory” one that “fell short of the requisite standard prescribed under the DSM-IV-TR”, especially since he, being the prosecution witness, would have much more available resources. Because of this, his testimony was held to be “less convincing” than that of the defence witness, who not only interviewed the accused in Hokkien, but also interviewed the accused person’s family members and the persons close to him.

[30] Eu Lim Hoklai, supra note 22.

[31] Eu Lim Hoklai, supra note 22 at [56]-[57].

[32] Eu Lim Hoklai, supra note 22 at [52] and [59].

The PDF version of this article is available for download here.

Obiter, Obiter, Obiter

by Lai Wei Kang, Louis


One of the ways lawyers come into their own is by honing the distinction between the ratio decidendi and obiter dicta of cases. This distinction is taught since the beginning of their arduous journey in law school, yet emphasized throughout their career as one of paramount importance. Obiter in the courtroom is often relegated and back-benched; counsel may demonstrate his wealth of knowledge, but succeeds only by distilling and employing ratio.

This article argues, contrary to the general observation of a humble freshman, that obiter should not be dismissed. The paradigm is that dicta is secondary, but just as rules are subject to exceptions, human paradigm is malleable to so much more; in many instances, dicta remains an invaluable form of judicial guidance. Furthermore, with recent developments and unique local circumstances, obiter dicta is likely to become invaluable.


Ratio decidendi is recognized as the section of judicial reasoning with direct correlation to material facts at hand.1 In a system of common law, it is widely recognized as the most valuable section of a judgment, and is the only part which binds lower courts in vertical stare decisis. Generally, the law avers from contemplating anything but the ratio: apart from making unnecessary complications in interpreting judgments, lawyers are taught that the law operates with analogical reasoning, and like cases must be decided alike. The most predictable result for a present case can only be drawn from another precedent that is “on all fours” with it; if favourable precedent is dissimilar from the present case in any way, the dissimilar facts must not concern the key reasoning behind judgment. The value that the law places on ratio is obvious from the devotion of legal practitioners in refining their skill of crystallizing the ratio decidendi of cases.

In contrast, students and practitioners of the law are incessantly reminded of the need – not only to omit – but to criticize and rebuke the use of obiter dicta. The obiter dicta of the judgment encompass every other part of the judgment not included within the ratio decidendi.2 Just as the ratio is persuasive in law, the obiter is rarely sufficient to convince; without direct bearing on the ultimate decision of the court, obiter are but commentary – passing remarks by judges that can be made without similar care to ratio.

This, however, does not seem true in any common law jurisdiction, and especially not in Singapore. The effort made by judges in commentary, both in their judicial capacity and in extra-judicial sitting, do not seem to commensurate with legal instinct that obiter is irrelevant. In fact, many of the advances made in substantial law are drawn from pure obiter, which have guided local courts in making decisions even before the opportunity to formulate a ratio arose.


Ratio decidendi faces limitations which obiter does not. In explaining the ratio decidendi of cases, judges adhere to the principles of legal precedents set before them, and strictly apply material fact to rule. As complex as it is promulgated thereafter, the ratio decidendi is essentially an input-output system. What elegant expression masks is legal machinery that makes binary decisions on minor tests.

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The persuasiveness of ratio is precisely due to and correlated with its limitations. Ratio is most powerful when it is restricted to key and analogous facts, and it is a fish out of water outside of such limited circumstances.

In contrast, the commentary made by judicial practitioners has wider applicability than the ratio decidendi of a case. Judges may consider the application of novel legal principles in alternative factual circumstances, (their opinion) on the disposition and direction of the law, and other comments they may have.3

At times, the decisive turn of a judgment may be found in dicta instead of its ratio decidendi. Where decisions are made and the arm of prevailing legal principle is twisted to achieve a just solution, obiter dicta may better explain the results achieved. For instance, the unsatisfactory state of the postal acceptance rule was not supplanted but circumvented in antecedent cases such as Holwell Securiities v Hughes4, where the generality may be excepted by specifically requiring “notice in writing” or would produce “manifest inconvenience and absurdity”. In effect, Holwell Securities v Hughes traced the dissent of Bramwell LJ in Household Fire & Carriage Accident Insurance Co Ltd v Grant5; the strenuous evasion of the tricky postal acceptance rule followed the expiration of policy considerations encouraging the use of postal delivery for contracts. Yet judges remain hesitant to remove a doctrine entrenched in the law of contract due to respect for the weight of precedent and fear of a vacuum left in the law of acceptance; thus, most of their deliberations are found in obiter.

In fact, the undisclosed rationale for decisions may easily be found in ostensibly unrelated comments and dicta. A novel application of psychological Freudian analysis to judgments6 discovered undercurrents to decisions, which were related to neither material fact nor legal principle. The authors found that judges could potentially “reach an early decision” before “iterating backwards…[to] an optimal solution to resolving the case”. Notwithstanding fervent hopes that such is anomalous, one cannot now discount the assistance that dicta provide in navigating to the heart of a judgment.


Often, ratio decidendi makes little sense without the obiter dictum. Obiter explains the ratio of the case in relation to judicial principles, and the ratio decidendi is not amply convincing without its obiter. At times, judges may even establish limits and exceptions to ratio in their remarks.7

In fact, judges make a conscious effort to deal with obiter. Rare is the instance where a judge remarks that another’s word are “just obiter” or “dicta”; and even on such occasions, judges do not disapprove the dicta of another on that basis alone. For instance, Megarry J denied a submission that comments could be dismissed on the basis of being mere dicta. He reinforced the position of dicta with “the highest authority that any dictum can bear”, classifying “a third type of dictum” which bore the authority not only of the judge’s own opinion, but that of “an unseen cloud of his judicial brethren”.8 The spirited defence above evinces wide recognition that dicta carries significant weight; the opinion of as learned a practitioner in law as a judge cannot be so sorely mistaken as to be waived with a simple label of “obiter”.

Furthermore, one cannot truly isolate the obiter. Much to the dismay of the concerted efforts of practitioners, there is no clear demarcation between the ratio and obiter of a case; the interpretation of judicial reasoning is as uncertain as it is human. What is thought to be circumstantial to one lawyer could have substantive value to another.

With multiple lines of reasoning, what takes the position of ratio can be contested. Will only one applicable line of reasoning be accepted as binding judicial precedent? Competing ratios may ultimately undermine the decisive value of ratio as well.


In the doctrine of judicial precedent, the use of ratio decidendi is purposed for a slow and careful development of the law. Although wariness is want in larger jurisdictions, slow development by analogy to past cases disadvantages smaller jurisdictions; opportunities to develop substantial law in one area may be limited by the regularity of cases coming forth. Judges may therefore use dictum to advance the law’s development; doing so is not incompatible with taking care in the law, and may be entirely justified by a plethora of considerations. For instance, where precedents differed over when consideration is provided for contract modifications, Arden LJ advanced an alternative idea of a “collateral unilateral contract” in MWB Business Exchange Centres Ltd v Rock Advertising Ltd9 to reconcile the precedents. While it may not have been necessary given that Kitchin LJ had not resorted to such a mechanism, the spate of dissonance welcomed a thorough effort to resolve it. One can hardly deny that the rules on “Himalaya clauses” developed in a similar fashion; the cases of The Eurymedon10 and The New York Star11 built on dicta left by Reid L in Scruttons v Midland Silicones12, fleshing out the solution for carriers seeking to protect their stevedores from liability to consigners. After all, the English courts have nothing to lose, and all to gain, from contemplating all viable options to open questions in law.

With the growth of alternatives to litigation in other forms of dispute resolution13 – most of which carry limited precedential value14 – common law jurisdictions may lose their source of incremental development. Under such circumstances, obiter may easily become more valuable.

Similarly, where the number of circumstances is limited – and desirably so – in a small jurisdiction like Singapore, obiter has significance since it is the quickest manner in which law can develop. Unlike larger jurisdictions which have had centuries of time to develop their laws with analogy and incremental development, states like Singapore with little more than half a century inevitably rely heavily on obiter dicta. In both Ngiam Kong Seng v Lim Chiew Hock15 and Man Mohan Singh s/o Jothirambal Singh v Zurich Insurance (Singapore) Pte Ltd16, the Singapore Court of Appeal applied the autochthonous legal test for a duty of care17 in full in spite of both claims having failed on the threshold requirement of factual foreseeability. Owing to the restricted size of jurisprudence, the honourable Judges of Appeal seized the opportunity to examine the application of Spandeck Engineering (S) Pte Ltd v Defence Science & Technology Agency in psychiatric injury claims. The distinction between primary and secondary victims of psychiatric injury18 would not have been removed from Singapore law but for Andrew Phang JA’s dicta. Obiter dictum could thus supplant ratio in developing the law when:

  • a. Obiter is used to explain the preferred route of the law in the future, where the ratio decidendi cannot because the case itself does not lend a factual matrix appropriate for a legal issue to be addressed.
  • b. Obiter is used to make up for the lack of situations in which a binding ratio decidendi can be formulated
  • c. Obiter provides the widest explanations of multiple answers in law, and therefore expedites the law’s incremental development


An American reference details that apart from the formal restrictions on dicta, dicta is sparingly used because “the reader may view its use as an attempt to misstate the law”.19 Perhaps the true concern of lawyers and judges alike is not truly against dicta being mere comments per se, but really against negligence and malice. Yet if this is the concern, our motivations to study obiter dicta should be stronger. While it would appease the rudimentary to know of ratio, a true and complete comprehension of the law cannot be achieved without reading dicta. If students, practitioners and critics of the law are to answer a calling above a vocation, then blindness to dicta will only cause us to fall short of our standards, and do injustice on those relying on our expertise.

[1] See Robert C. Beckman, Brady S. Coleman, Joel Lee, Case Analysis and Statutory Interpretation, (Singapore: National University of Singapore Faculty of Law), 76 for the definition ofratio. Further, the authors provide ample warning at p 63 that “the rule of law stated in a case…may not incorporate the material facts…[students] must be cautious and not assume that this wide proposition of law will be accepted as the ratio decidendi”.

[2] Ibid at 65, where obiter is referred to as “statements in a judgment which are not part of the decision, but which nevertheless are important”; at p 76 such significance is then redacted to being “at the most persuasive”.

[3] Ibid at 65, dicta assists in “predicting how related issues might be decided in subsequent cases”, especially when a noteworthy judge provides insight that “are not necessary to the decision in the present case”, or set “possible limits or exceptions” to the ratio.

[4] [1974] 1 All ER 161.

[5] [1879] 4 Ex C 216.

[6] Foo Check Teck, “Freudian Analysis of a Judgment”, Singapore Law Gazette (7 February 2003) (

[7] Supra note 3.

[8] Richard West and Partners v Dick [1969] 2 WLR 383 at 388A-D.

[9] [2016] EWCA Civ 553 at [89]. By devising a “collateral unilateral contract” over existing contracts, Professor Mindy Chen-Wishart’s device as borrowed could resolve a dispute over whether an agreement to accept payment by instalment was enforceable under consideration. This dispute recognizably plagued English Law since precedents of In re Selectmove [1995] 1 WLR 474 and Williams v Roffey Brothers [1991] 1 QB 1 were diametrically opposed on the issue.

[10] [1975] AC 154.

[11] [1980] 3 All ER 257.

[12] [1962] AC 446 at 472-479.

[13] The growth of alternative dispute resolution mechanisms (“ADR”), especially in Singapore, can be taken as trite. Notwithstanding the variety of reports, even leading textbooks recognize that ADR has seen “phenomenal development” and “is set to become an undeniable aspect of the Singapore legal system”. (Supra note 1 at 39).

[14] The rare instances in which alternative dispute resolution mechanisms have binding authority are when they are subject to judicial review: for example, see Clea Shipping Corp. v Bulk Oil International Ltd [1983] 2 Lloyd's Rep 646, where the Queen’s Bench considered and agreed on the arbitral decision.

[15] [2008] 3 SLR(R) 674.

[16] [2008] 3 SLR(R) 735.

[17] Often and affectionately called the Spandeck test, as derived from Spandeck Engineering (S) Pte Ltd v Defence Science & Technology Agency [2007] 4 SLR(R) 100.

[18] Originating from Page v Smith [1995] UKHL 7.

[19] Richard K. Neumann, Jr., Kristen Konrad Tiscione, Legal Reasoning and Legal Writing, 7th ed, 90.

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