SERENE TIONG SZE YIN v CHAN HERNG NIENG

"Having regard to the totality of the circumstances and the evidence before me, I find that Dr Chan did not act in breach of the general professional standard when he gave Xanax to Ms Tiong, his then-girlfriend, without registering her as his patient." — Per Tan Siong Thye J, Para 81

Case Information

• Citation: [2022] SGHC 170 (Para 0)
• Court: General Division of the High Court of the Republic of Singapore (Para 0)
• Date: 19 July 2022 (Para 0)
• Coram: Tan Siong Thye J (Para 0)
• Case Number: Suit No 400 of 2020 (Para 0)
• Area of Law: Tort — Negligence — Breach of duty; Tort — Negligence — Duty of care; Tort — Rule in Wilkinson v Downton (Para 0)
• Counsel for the plaintiff: Not answerable from the extraction provided (NOT ANSWERABLE)
• Counsel for the defendant: Not answerable from the extraction provided (NOT ANSWERABLE)
• Judgment Length: Not answerable from the extraction provided (NOT ANSWERABLE)

Summary

This case arose from a deeply personal dispute between a psychiatrist and his former intimate partner, Ms Tiong, and the court expressly characterised it as “a lover’s spat.” The plaintiff alleged that Dr Chan negligently supplied her with Xanax during their relationship and also advanced a claim under the rule in Wilkinson v Downton. The court ultimately rejected both claims, holding that Dr Chan did not breach the general professional standard and that the Wilkinson claim failed. (Para 4) (Para 81)

The negligence analysis turned on whether a reasonably experienced psychiatrist in Dr Chan’s position would have administered Xanax to Ms Tiong, how many tablets were given, whether addiction was foreseeable, and whether any breach caused actionable harm. The court approached those issues through the ordinary negligence framework, the medical-negligence authorities in Bolam and Bolitho, and the Singapore Court of Appeal’s guidance in Hii Chii Kok. It also treated the Ethical Code and Ethical Guidelines as important but not mechanically determinative. (Para 40) (Para 43) (Para 45) (Para 51)

On the facts, the court placed substantial weight on contemporaneous WhatsApp communications, the evidence of the joint expert Dr Lim, and the internal inconsistencies in Ms Tiong’s account of when Xanax was first supplied. The court found that the messages did not support her version of events and that her evidence on a crucial pillar of the case was “gravely inconsistent and irreconcilable.” Those credibility findings materially shaped the outcome of both the negligence and Wilkinson claims. (Para 86) (Para 91)

How did the court characterise the dispute at its core?

The court began by situating the litigation in its human context, but it did so in a way that was plainly sceptical of the plaintiff’s framing. It observed that the case was not a conventional medical-negligence dispute between strangers in a clinical setting; rather, it concerned a psychiatrist and his then-girlfriend, with the alleged treatment occurring against the backdrop of an intimate relationship. That framing mattered because it informed the court’s assessment of the parties’ conduct, the ethical guidelines, and the credibility of the competing narratives. (Para 4) (Para 42)

"This case is, at its core, a lover’s spat." — Per Tan Siong Thye J, Para 4

The court also noted that the plaintiff’s claim was that Dr Chan acted in breach of his duty of care to her as his de facto patient when he gave her Xanax, which she described as an addictive drug classified as poison under the Poisons Act. That allegation was central to the negligence claim, because it sought to convert a relationship-based exchange of medication into a professional breach of duty. The court’s later reasoning shows that it did not accept that the relationship alone established negligence. (Para 5) (Para 81)

In addition, the court’s narrative made clear that the dispute had already generated other litigation and regulatory or quasi-regulatory events, including a police warning, a defamation suit, and a derivative action. Those surrounding proceedings formed part of the background against which the court assessed the parties’ credibility and the broader context of their relationship breakdown. (Para 13) (Para 20) (Para 21) (Para 22) (Para 23)

What were the key facts leading up to the breakdown of the relationship?

The relationship began after the parties met in December 2016 and became intimate in or around January 2017. The court accepted that the relationship was not merely social but romantic and sexual, and it treated that fact as foundational to the later dispute over medication and alleged inducement. The relationship later deteriorated after Ms Tiong discovered WhatsApp messages in April 2018 that revealed Dr Chan’s infidelity. (Para 9) (Para 10)

"After the first meeting in December 2016, Ms Tiong and Dr Chan started an intimate relationship in or around January 2017." — Per Tan Siong Thye J, Para 9

The court recorded that on or around the night of 22 April 2018, while Dr Chan was asleep, Ms Tiong unlocked his mobile phone using his thumbprint. That event was important because it led to the discovery of messages that triggered the collapse of the relationship and, in the court’s view, formed part of the factual matrix explaining the later litigation. The court treated the discovery as the turning point in the parties’ relationship. (Para 10) (Para 12)

"On or around the night of 22 April 2018, while Dr Chan was asleep, Ms Tiong unlocked Dr Chan’s mobile phone using his thumbprint." — Per Tan Siong Thye J, Para 10

The court then stated that this marked the end of the relationship. It also noted that during the relationship Dr Chan gave Ms Tiong Xanax tablets to help her cope with anxiety. That fact was not disputed in the abstract; the dispute was about the circumstances, quantity, purpose, and professional significance of the supply. (Para 12) (Para 14)

"This marked the end of Ms Tiong and Dr Chan’s relationship." — Per Tan Siong Thye J, Para 12

"During their relationship, Dr Chan gave Ms Tiong Xanax tablets to help her cope with her anxiety." — Per Tan Siong Thye J, Para 14

What negligence issues did the court identify for trial?

The court framed the negligence claim around a series of concrete questions rather than a broad abstract complaint. It asked whether a reasonably experienced psychiatrist in Dr Chan’s position, who was in an intimate relationship with Ms Tiong, would administer Xanax to her; how many tablets were given and over what period; whether Dr Chan should have foreseen that Ms Tiong would become dependent on Xanax; and whether any breach caused harm. This structure shows that the court treated breach, causation, and harm as distinct analytical steps. (Para 40)

"The main issues regarding the claim that Dr Chan breached his duty of care to Ms Tiong are as follows: (a) Would a reasonably experienced psychiatrist in Dr Chan’s position (ie, who was in an intimate relationship with Ms Tiong) administer Xanax to Ms Tiong? (b) How many tablets of Xanax did Dr Chan give to Ms Tiong, and across what period of time?" — Per Tan Siong Thye J, Para 40

The court also identified the foreseeability of addiction and the existence of harm as separate issues. That is significant because the plaintiff’s case was not merely that Xanax was given, but that it was given in a way that created dependency or other injury. The court’s formulation indicates that it was prepared to test the claim against the ordinary negligence elements rather than assume that any supply of a controlled medication in a personal relationship was automatically wrongful. (Para 40) (Para 43)

In the same section, the court also identified the Wilkinson claim issues. It asked whether Dr Chan made the alleged Statement, whether Ms Tiong was induced by it to enter into or continue the sexual relationship, whether Dr Chan intended to cause psychiatric harm, and whether psychiatric harm resulted. The court therefore treated the Wilkinson claim as a separate tort with its own factual and mental-element inquiries, not as a mere appendage to the negligence claim. (Para 41)

"The main issues regarding the claim under the rule in Wilkinson are as follows:67 (a) Did Dr Chan make the Statement? (b) Was Ms Tiong induced by the Statement to enter into and/or continue with their sexual relationship?" — Per Tan Siong Thye J, Para 41

How did the court approach the general negligence framework and the medical standard of care?

The court began from the orthodox negligence framework. It stated that a claimant must prove duty of care, breach, causation, remoteness, and provable loss. This was not controversial in the abstract, but it mattered because the plaintiff’s case depended on showing that Dr Chan’s conduct fell below the required standard and that the alleged breach caused actionable harm. The court’s articulation of the elements anchored the rest of the analysis. (Para 43)

"It is axiomatic that to establish a claim under the tort of negligence, the claimant must demonstrate that (a) the defendant owes the claimant a duty of care; (b) the defendant breaches this duty of care by acting (or omitting to act) below the standard of care required of him; (c) the defendant’s breach of duty caused the claimant to suffer losses; (d) the claimant’s losses are not too remote; and (e) such losses can be adequately proved and quantified." — Per Tan Siong Thye J, Para 43

For medical negligence, the court relied on Bolam and Bolitho, and it expressly noted the Court of Appeal’s holding in Hii Chii Kok that the Bolam-Bolitho test applies to diagnosis and treatment. The court also explained the Bolitho addendum as a two-stage inquiry: whether the expert opinion addressed comparative risks and benefits, and whether the opinion was defensible, meaning internally consistent and not contradicted by proven extrinsic facts. That discussion shows that the court was attentive to both professional judgment and rational defensibility. (Para 45)

"The Bolitho addendum consists of a two-stage inquiry of, first, whether the experts holding the opinion had directed their minds to the comparative risks and benefits relating to the matter, and second, whether the opinion was defensible (meaning that it was internally consistent and did not contradict proven extrinsic facts relevant to the matter)." — Per Tan Siong Thye J, Para 45

The court then linked those principles to the ethical framework governing doctors. It observed that the Ethical Code and Ethical Guidelines were not to be treated as a rigid code that automatically determined negligence. Instead, they were guides to professional judgment. This distinction was central to the court’s conclusion that a breach of the guidelines would not necessarily amount to a breach of the general professional standard. (Para 50) (Para 51)

"We agree that in general, a doctor may and should depart from guidelines when there are good reasons for him to do so. A doctor ought not to suspend his clinical judgment, simply because there are guidelines which, after all, are plainly not intended for slavish adherence, but are there to assist and guide a doctor in the exercise of his clinical judgment." — Per Tan Siong Thye J, Para 50

"A breach of the ECEG does not ipso facto lead to the automatic conclusion that a doctor has acted in breach of the general professional standard, though it may suggest that the general professional standard may not have been complied with." — Per Tan Siong Thye J, Para 51

What did the parties argue about the Xanax prescription and the ethical guidelines?

Ms Tiong’s case was that Dr Chan supplied Xanax and Trazodone in a “free and easy manner” for recreational rather than prescriptive use. She also contended that Dr Chan failed to register her as a patient, failed to conduct a proper assessment, and failed to warn her about the risks. The thrust of her case was that the supply of medication in the context of a romantic relationship was professionally improper and negligent. (Para 24)

"Ms Tiong argues that Dr Chan supplied Xanax and Trazodone, which is also listed in the Schedule to the Poisons Act, to her in a ‘free and easy manner’ for ‘recreational, rather than prescriptive, use’." — Per Tan Siong Thye J, Para 24

Dr Chan’s response was that Xanax was suitable for Ms Tiong’s consumption. He relied, among other things, on the fact that subsequent psychiatrists prescribed Xanax to her after the relationship ended, and he argued that the quantity he gave was limited. He also relied on the expert evidence and the ethical guidelines to contend that his conduct fell within permissible professional judgment. (Para 33) (Para 66)

"Dr Chan argues that Xanax was indeed suitable for Ms Tiong’s consumption, based on, inter alia, the following: (a) Ms Tiong was prescribed Xanax by subsequent psychiatrists that she consulted after the fallout of her relationship with Dr Chan sometime end of May 2018." — Per Tan Siong Thye J, Para 33

The court’s treatment of these competing positions was not to ask whether the relationship was ideal from an ethical standpoint in the abstract, but whether the evidence established a breach of the general professional standard. The court ultimately answered that question in the negative, emphasising the totality of the circumstances and the evidence before it. (Para 81)

Why did the court reject the plaintiff’s account of when Xanax was first supplied?

A major part of the court’s reasoning concerned the chronology of Xanax supply. The court found that Ms Tiong’s evidence on this “crucial pillar” of her case was gravely inconsistent and irreconcilable. That finding was not a peripheral credibility comment; it went directly to the alleged breach, because the timing and circumstances of the first supply of Xanax were central to whether Dr Chan’s conduct was negligent. (Para 86)

"Ms Tiong’s evidence on this crucial pillar of her case was gravely inconsistent and irreconcilable." — Per Tan Siong Thye J, Para 86

The court also relied on the WhatsApp messages. It noted that the messages at the relevant point were sent when Ms Tiong was taking medication to help her sleep, and that there was no reference to Xanax in those communications, although there were extensive references to other drugs. This mattered because the absence of Xanax references in contemporaneous communications undermined the plaintiff’s attempt to prove that Xanax had already been supplied in the manner she alleged. (Para 91)

"The WhatsApp messages at [90] above were sent when Ms Tiong was taking medication to help her sleep. There was no reference to Xanax in the communications, although there were extensive references to other drugs." — Per Tan Siong Thye J, Para 91

In practical terms, the court used the contemporaneous messages to test the reliability of the oral evidence. The result was that the plaintiff’s narrative did not withstand scrutiny against the documentary record. That credibility assessment fed into the broader conclusion that the plaintiff had not established breach on the evidence. (Para 86) (Para 91) (Para 81)

How did the court treat the expert evidence and the ethical rules governing doctors?

The court referred to the evidence of Dr Lim, who addressed the ethical rules binding medical professionals and the risks of Xanax consumption, including the chances of addiction. The expert evidence was relevant because the case turned in part on whether a psychiatrist in Dr Chan’s position would have acted outside the range of acceptable professional judgment. The court’s analysis shows that it did not treat the expert evidence as dispositive in isolation; rather, it considered it alongside the factual matrix and the documentary evidence. (Para 39) (Para 45)

"Dr Lim gave evidence on, inter alia, the applicable ethical rules binding medical professionals like Dr Chan and the risks of Xanax consumption, including the chances of addiction." — Per Tan Siong Thye J, Para 39

The court’s discussion of the ECEG was especially important. It accepted that the guidelines were relevant, but it emphasised that they were not a rigid code whose breach automatically established negligence. It also relied on authority stating that doctors may and should depart from guidelines when there are good reasons to do so, because the guidelines are meant to assist clinical judgment rather than replace it. That reasoning allowed the court to assess Dr Chan’s conduct in context rather than by a purely formalistic rule. (Para 50) (Para 51)

On that basis, the court concluded that Dr Chan’s prescription of Xanax fell within the permissive rule in ECEG Guideline B1.5. The significance of that conclusion is that the court did not regard the intimate relationship as, by itself, making the prescription professionally impermissible on the facts proved. Instead, it treated the relationship and the limited supply as part of the totality of circumstances supporting the absence of breach. (Para 66) (Para 81)

"Accordingly, Dr Chan’s prescription of Xanax to Ms Tiong falls within the permissive rule in ECEG Guideline B1.5." — Per Tan Siong Thye J, Para 66

How did the court resolve the negligence claim?

The court’s conclusion on negligence was explicit and categorical. After reviewing the circumstances and the evidence, it held that Dr Chan did not breach the general professional standard when he gave Xanax to Ms Tiong without registering her as his patient. That holding was the central ratio of the case on the negligence issue. It reflects the court’s acceptance that the conduct, though unusual, was not shown to be professionally negligent on the evidence before it. (Para 81)

"Having regard to the totality of the circumstances and the evidence before me, I find that Dr Chan did not act in breach of the general professional standard when he gave Xanax to Ms Tiong, his then-girlfriend, without registering her as his patient." — Per Tan Siong Thye J, Para 81

The court’s reasoning leading to that conclusion can be traced through several linked propositions. First, the negligence standard required proof of breach, not merely impropriety or discomfort with the relationship context. Second, the ethical guidelines were relevant but not conclusive. Third, the plaintiff’s factual account of the Xanax supply was undermined by inconsistency and contemporaneous messages. Fourth, the expert evidence and the surrounding circumstances supported the view that the prescription fell within permissible professional judgment. (Para 43) (Para 50) (Para 51) (Para 66) (Para 86) (Para 91)

Accordingly, the court did not need to find that Dr Chan’s conduct was ideal or exemplary; it only needed to decide whether the plaintiff had proved a breach of the applicable standard. It found that she had not. That conclusion disposed of the negligence claim. (Para 81)

What was the Wilkinson v Downton claim and why did it fail?

The court treated the Wilkinson claim as a separate cause of action requiring proof of a statement, inducement, intention to cause psychiatric harm, and actual psychiatric harm. The plaintiff’s case was that Dr Chan made a false Statement to induce or maintain the sexual relationship. The court’s framing shows that it understood the claim as one based on intentional infliction of harm through a false statement, not merely on the existence of a deceitful relationship. (Para 41)

"The main issues regarding the claim under the rule in Wilkinson are as follows:67 (a) Did Dr Chan make the Statement? (b) Was Ms Tiong induced by the Statement to enter into and/or continue with their sexual relationship?" — Per Tan Siong Thye J, Para 41

The extraction provided does not reproduce the full Wilkinson analysis section, but it does show that the court ultimately rejected the claim. The structure of the issues indicates that the court required proof of both the making of the Statement and its causal effect on the relationship, as well as the necessary mental element and harm. The absence of a successful finding on the underlying factual and credibility issues would have been fatal to the claim. (Para 41) (Para 81)

In practical terms, the same credibility concerns that undermined the negligence claim also weakened the Wilkinson claim. If the plaintiff could not reliably establish the factual basis for her account of the medication and relationship dynamics, it would be difficult to prove the alleged Statement and its alleged effect. The court therefore rejected the Wilkinson claim alongside the negligence claim. (Para 86) (Para 91) (Para 81)

Why did the court mention the plaintiff’s other litigation and police warning?

The court included background about a police warning in lieu of prosecution for attempted extortion under s 385 of the Penal Code, a defamation suit, and a statutory derivative action. These matters were not the direct subject of the negligence claim, but they formed part of the broader factual context in which the parties’ relationship and credibility were assessed. The court’s inclusion of them suggests that it considered the litigation history relevant to understanding the parties’ interactions and the plaintiff’s approach to dispute escalation. (Para 13) (Para 20) (Para 21) (Para 22) (Para 23)

"On 15 January 2020, the Singapore Police Force (‘SPF’) issued Ms Tiong a written warning in lieu of prosecution for the offence of attempted extortion under s 385 of the Penal Code (Cap 224, 2008 Rev Ed) (‘the Penal Code’)." — Per Tan Siong Thye J, Para 13

The court also referred to the defamation proceedings, noting that the district judge had initially dismissed Dr Ong’s libel claim on justification grounds, but that the appeal later found Ms Tiong failed in that defence. It further referred to the derivative action suit and the Court of Appeal’s description of the claim as wholly unmeritorious. These references were not themselves holdings in the present case, but they show the court’s awareness of the wider litigation history between the parties and related actors. (Para 20) (Para 22) (Para 23)

"In the Defamation Suit, the district judge (“DJ”) dismissed Dr Ong’s claim in libel on the basis that Ms Tiong had successfully proven the defence of justification." — Per Tan Siong Thye J, Para 20

"In Ong Kian Peng Julian v Tiong Sze Yin Serene [2021] 3 SLR 980 (“the Defamation Appeal”), See Kee Oon J found at [85] that Ms Tiong failed in her defence of justification." — Per Tan Siong Thye J, Para 20

"In Tiong Sze Yin Serene v HC Surgical Specialists Ltd and another [2020] SGHC 201 (“the Derivative Action Suit”), Chua Lee Ming J dismissed the application." — Per Tan Siong Thye J, Para 22

"In Civil Appeal No 129 of 2020 (“CA 129”), the Court of Appeal upheld Chua J’s decision to dismiss Ms Tiong’s claim, finding that Ms Tiong’s claim was “wholly unmeritorious”." — Per Tan Siong Thye J, Para 23

Why does this case matter?

This case matters because it clarifies how Singapore courts may approach negligence allegations arising in an unusual relational setting, namely where a doctor and the claimant are also intimate partners. The court made clear that the existence of a romantic relationship does not automatically transform a medical or quasi-medical interaction into negligence. Instead, the claimant must still prove breach of the applicable standard, and the court will assess the evidence, the expert material, and the ethical guidelines in context. (Para 42) (Para 43) (Para 50) (Para 51) (Para 81)

The case is also important for its treatment of professional guidelines. The court’s reasoning confirms that ethical guidelines are highly relevant but not self-executing rules of liability. That distinction is practically significant for medical practitioners, because it preserves room for clinical judgment while still allowing guidelines to inform the standard of care. (Para 50) (Para 51) (Para 66)

Finally, the judgment is notable for its credibility analysis. The court relied on contemporaneous communications and found the plaintiff’s evidence on a crucial issue to be gravely inconsistent and irreconcilable. For litigators, the case is a reminder that where a claim depends on a contested chronology, documentary evidence may be decisive, and credibility findings can determine the outcome across multiple causes of action. (Para 86) (Para 91) (Para 81)

"The present case involves an interesting application of otherwise trite tort law principles, ie, the duty of care owed by a doctor to his patient who is simultaneously his paramour." — Per Tan Siong Thye J, Para 42

Cases Referred To

Legislation Referenced

• Poisons Act (Cap 234, 1999 Rev Ed) — referenced in relation to Xanax being classified as poison and the plaintiff’s negligence theory. (Para 5)
• Penal Code (Cap 224, 2008 Rev Ed), s 385 — referenced in connection with a written warning for attempted extortion. (Para 13)
• Companies Act (Cap 50, 2006 Rev Ed), s 216A(2) — referenced in the derivative action background. (Para 21)
• Misuse of Drugs Act 1973 — referenced in the extraction as part of the judgment’s statutory references, but no specific section is provided in the excerpt. (NOT ANSWERABLE beyond the statute’s mention)

Source Documents

• Original Judgment — Singapore Courts
• Archived Copy (PDF) — Litt Law CDN

This article analyses [2022] SGHC 170 for legal research and educational purposes. It does not constitute legal advice. Readers should consult the full judgment for the Court's complete reasoning.