Tan Hai Peng Micheal and another (as the executors of the estate of Tan Thuan Teck, deceased) v Tan Cheong Joo and another and other matters

Case Details

• Citation: [2026] SGHC 49
• Court: General Division of the High Court of the Republic of Singapore
• Decision Date: 6 March 2026
• Coram: S Mohan J
• Case Number: Originating Claim No 381 of 2023; Originating Claim No 382 of 2023; Originating Claim No 201 of 2024
• Hearing Date(s): 10, 18 September, 18 November, 3, 9, 15 December 2025
• Claimants / Plaintiffs: Tan Hai Peng Micheal; Tan Hai Seng Benjamin (as the executors of the Estate of Tan Thuan Teck, deceased)
• Respondents / Defendants: Tan Cheong Joo; Tan Seong Kok; Tan Siong Tiew; Tan Siong Lim; Fong Tat Holding Co Pte Ltd
• Counsel for Claimants: Yeoh Kar Hoe, Ng Wei Jin and Abel George (David Lim & Partners LLP)
• Counsel for Respondents: Goh Peck San (P S Goh & Co)
• Practice Areas: Civil Procedure; Costs; Artificial Intelligence; Legal Ethics

Summary

The decision in Tan Hai Peng Micheal and another v Tan Cheong Joo and another [2026] SGHC 49 serves as a seminal warning to the Singapore legal profession regarding the non-delegable duties of advocates and solicitors in the age of Generative Artificial Intelligence (“GenAI”). This judgment is the procedural and costs-focused sequel to the court’s earlier determination on the merits in [2025] SGHC 217 (the “First Judgment”), where the claimants, acting as executors of the estate of the late Tan Thuan Teck (“TTT”), successfully established the defendants’ liability for various outstanding loans.

The central controversy in the present proceedings, termed the “Fictitious Authorities Issue,” arose when the defendants’ closing submissions were found to contain citations to two non-existent legal authorities. One authority (“Case A”) utilized a real case name but a neutral citation belonging to an entirely different matter, while the second (“Case B”) featured both a fictitious name and a fictitious citation. Neither “case” supported the legal propositions for which they were cited. The court was tasked with determining the appropriate costs consequences, specifically whether personal costs orders should be made against the defendants’ counsel, Mr. Goh Peck San, and an assisting solicitor, Mr. Amarjit Singh Sidhu, who had been engaged to perform research and drafting tasks.

S Mohan J applied the three-stage test from Ridehalgh v Horsefield [1994] Ch 205 to evaluate whether the solicitors’ conduct was improper, unreasonable, or negligent. The court held that the citation of fictitious authorities, whether resulting from blind reliance on GenAI or inadequate supervision of subordinates, constitutes a serious breach of the duty to the court. The judgment clarifies that the responsibility to verify the authenticity and accuracy of cited authorities is personal to the solicitor on record and cannot be delegated to junior staff, paralegals, or external research assistants. Furthermore, the court extended the definition of “solicitor” under the Legal Profession Act 1966 to encompass assisting solicitors who are not formally on record but whose conduct contributes to the wasted costs.

Ultimately, the court fixed global costs for the suits at $180,000 and imposed personal costs orders against both Mr. Goh and Mr. Sidhu. This decision reinforces the principle that while GenAI may be a tool for efficiency, it does not diminish the professional standards required of the Bar. The administration of justice relies on the accuracy of submissions, and the court will not hesitate to exercise its inherent and statutory powers to penalize conduct that undermines this foundation.

Timeline of Events

1. 6 June 2025: Procedural milestone or hearing date related to the lead-up of the substantive trial.
2. 2 July 2025: Further procedural date in the management of the consolidated suits.
3. 7 July 2025: Key date in the pre-trial phase of the litigation.
4. 4 August 2025: Commencement of specific trial-related filings or hearings.
5. 15 August 2025: Interim procedural deadline or hearing date.
6. 26 August 2025: Final preparations for the September evidentiary hearings.
7. 4 September 2025: Significant hearing date involving the parties and their respective counsel.
8. 10 September 2025: Commencement of the substantive hearing block before S Mohan J.
9. 11 September 2025: Continuation of the substantive hearing and evidentiary proceedings.
10. 12 September 2025: Conclusion of the initial September hearing block.
11. 17 September 2025: Filing of further documents or interim hearing.
12. 18 September 2025: Resumption of the substantive hearing.
13. 4 November 2025: Post-trial procedural date or deadline for submissions.
14. 18 November 2025: Further substantive hearing date focused on closing arguments or specific issues.
15. 2 December 2025: Filing or hearing regarding the Fictitious Authorities Issue.
16. 3 December 2025: Continuation of the hearing block in December.
17. 9 December 2025: Further hearing date addressing costs and procedural misconduct.
18. 15 December 2025: Final hearing date for the substantive and costs-related matters.
19. 6 March 2026: Delivery of the judgment in [2026] SGHC 49.

What Were the Facts of This Case?

The litigation originated from a series of loan transactions between the late Tan Thuan Teck (“TTT”) and the defendants. The defendants included four brothers—Tan Cheong Joo, Tan Seong Kok, Tan Siong Tiew, and Tan Siong Lim—and their family-controlled entity, Fong Tat Holding Co Pte Ltd. Following TTT’s passing, the claimants, Tan Hai Peng Micheal and Tan Hai Seng Benjamin, acting as executors of TTT’s estate, sought to recover the outstanding balances of these loans. Three separate actions were commenced: Originating Claim No 381 of 2023, Originating Claim No 382 of 2023, and Originating Claim No 201 of 2024. These suits involved substantial sums, with specific claims including amounts such as $330,989.26, $108,803.77, $115,805.16, and $106,380.33.

The defendants raised various defences, including the argument that TTT was an unlicensed moneylender under the Moneylenders Act (Cap 188, 2010 Rev Ed). However, in the First Judgment ([2025] SGHC 217), S Mohan J found in favor of the claimants, ruling that the loans were enforceable and that the defendants had failed to substantiate their defences. The court then moved to the assessment of costs, which was complicated by a significant breach of professional conduct by the defendants’ legal team.

During the closing submissions phase, the defendants’ counsel, Mr. Goh Peck San, filed a written submission that cited two legal authorities that did not exist. “Case A” was cited as Tan v Tan [2015] SGHC 182. While the name Tan v Tan is common in Singapore jurisprudence, the neutral citation [2015] SGHC 182 actually refers to the case of Lau Siew Ngoh v SML Shipyard Pte Ltd. “Case B” was cited as Lim v Koh [2018] SGHC 250, a case name and neutral citation that were entirely fictitious. These citations were used to support a critical legal argument regarding the burden of proof under the Moneylenders Act, specifically whether the burden lay on the claimants to prove TTT was an “excluded moneylender.”

The claimants’ counsel, upon attempting to verify these authorities, discovered they were non-existent and raised the issue in their reply submissions. This prompted an investigation by the court. Mr. Goh explained that he had engaged an external solicitor, Mr. Amarjit Singh Sidhu, to assist with the research and drafting of the closing submissions. Mr. Sidhu, in turn, revealed that the research had been performed by a paralegal in his firm who had since left. Mr. Sidhu admitted that he had reviewed the draft but failed to verify the citations on LawNet or any other legal database. He conceded that he “overlooked” the fact that the cases could not be located and did not appreciate that they were not on point.

The court noted that the nature of the errors—specifically the creation of a plausible but fake neutral citation and the hallucination of a case name—bore the hallmarks of GenAI “hallucinations.” Although the solicitors did not explicitly admit to using GenAI, the court found that the failure to verify the authorities amounted to a gross departure from professional standards. The investigation into this issue required multiple rounds of further submissions and additional hearing dates, including sessions on 2, 3, 9, and 15 December 2025, thereby increasing the costs of the litigation significantly.

What Were the Key Legal Issues?

The court identified several critical legal issues arising from the Fictitious Authorities Issue, primarily centered on the court’s power to regulate the conduct of solicitors and the imposition of costs:

• The Application of Order 21 Rule 6 of the Rules of Court 2021: Whether the court should exercise its power to order a solicitor to personally pay costs that were “incurred improperly, unreasonably or negligently” or were “wasted by undue delay or by any other misconduct or default.”
• The Ridehalgh Three-Stage Test: How the established test for wasted costs orders should be applied to the citation of fictitious authorities. This involved determining:
  1. Whether the solicitor acted improperly, unreasonably, or negligently;
  2. Whether such conduct caused the other party to incur unnecessary costs; and
  3. Whether it is just in all the circumstances to order the solicitor to compensate that party.
• The Scope of the Term “Solicitor”: Whether Mr. Sidhu, who was not the solicitor on record but was an assisting solicitor, fell within the ambit of the court’s jurisdiction to make personal costs orders under the Legal Profession Act 1966 and the Rules of Court.
• The Non-Delegable Duty of Verification: Whether a solicitor on record can escape liability for fictitious citations by claiming reliance on an assisting solicitor, a paralegal, or an AI tool.
• The Impact of GenAI on Professional Negligence: Defining the standard of care for solicitors using AI-assisted research tools and whether “blind reliance” on such tools per se constitutes negligence.

How Did the Court Analyse the Issues?

S Mohan J began the analysis by emphasizing the gravity of citing fictitious authorities. He noted that the administration of justice is a “solemn and serious undertaking” and that the court relies on the “absolute integrity” of the materials presented by counsel. The citation of non-existent cases is not merely a technical error but a fundamental breach of the duty to the court.

The Ridehalgh Test: Stage 1 (Improper, Unreasonable, or Negligent Conduct)

The court applied the definitions from Ridehalgh v Horsefield [1994] Ch 205. “Improper” conduct includes any conduct which would ordinarily be held to justify disbarment or striking off. “Unreasonable” conduct is that which is vexatious or designed to harass. “Negligent” conduct is a failure to act with the competence reasonably to be expected of ordinary members of the profession.

Regarding Mr. Goh (the solicitor on record), the court found his conduct negligent. As the person who signed and filed the submissions, he bore the “ultimate responsibility” to check the veracity of the authorities. The court held at [61]:

“Mr Goh bore the ultimate responsibility to properly check the veracity and accuracy of the submissions before filing them with the court.”

Regarding Mr. Sidhu (the assisting solicitor), the court found his conduct also fell below the required standard. He had reviewed the draft prepared by the paralegal but failed to check the LawNet database when he could not find the cases. The court rejected the notion that he could simply pass on research without verification. The court noted that even if the use of AI was not explicitly admitted, the “blind reliance” on unverified research—whether human or machine-generated—was unreasonable and negligent.

The Ridehalgh Test: Stage 2 (Causation)

The court found that the citation of Case A and Case B directly caused the claimants to incur unnecessary costs. The claimants’ counsel had to spend time searching for the non-existent cases and then addressing the issue in their reply submissions. Furthermore, the court had to convene additional hearings and issue directions to investigate the matter. The court noted that the Fictitious Authorities Issue resulted in an “expenditure of time and resources that could not be said to be trivial” (at [55]).

The Ridehalgh Test: Stage 3 (Justice of the Order)

The court considered whether it was just to make the order. It took into account the solicitors’ apologies but balanced this against the need to protect the integrity of the judicial process. The court emphasized that the solicitors’ conduct was a “serious lapse” that went to the heart of the advocate’s duty. The court also considered the English decision in Ayinde v London Borough of Haringey [2025] 1 WLR 5147 and the Singapore decision in Tajudin bin Gulam Rasul v Suriaya bte Haja Mohideen [2025] 5 SLR 518, both of which dealt with fictitious authorities and emphasized the need for personal accountability.

The Definition of “Solicitor”

A key procedural point was whether the court could order Mr. Sidhu to pay costs personally, given he was not the solicitor on record. The court looked at s 2 of the Legal Profession Act 1966, which defines a “solicitor” as any solicitor of the Supreme Court. The court concluded at [35]:

“On this basis, the term ‘solicitor’ would, in my view, be wide enough to include Mr Sidhu, even if he was not the solicitor on record for the Defendants in the Suits.”

This interpretation ensures that all solicitors involved in the preparation of court materials are held to the same ethical and professional standards, regardless of their formal role on the record.

The Non-Delegable Duty and GenAI

The court was particularly firm on the issue of delegation. It held that the duty to verify authorities is non-delegable. Whether a solicitor uses a junior associate, a paralegal, or a GenAI tool like ChatGPT, the solicitor who presents the work to the court is personally responsible for its accuracy. The court warned at [42] that “not only is it unreasonable for a solicitor to be blindly reliant on AI-generated authorities, if the solicitor fails to verify the accuracy of all cases put before the court, such failure would also amount to negligent conduct.”

What Was the Outcome?

The court issued a comprehensive set of orders addressing both the general costs of the suits and the specific costs arising from the Fictitious Authorities Issue. The operative paragraph of the judgment states:

82. For the foregoing reasons, these are my orders:
(a) costs of the Suits are fixed at the global sum of $180,000 (excluding disbursements), payable to the Claimants;
...
(g) interest on the costs ordered is payable at the rate of 5.33% per annum from the date of this judgment to the date of payment.

The global sum of $180,000 was determined based on the complexity of the three consolidated suits and the length of the trial. However, the court specifically carved out the liability for these costs to reflect the solicitors’ misconduct. The court ordered that:

• Personal Liability: Mr. Goh and Mr. Sidhu were ordered to personally pay a portion of the costs directly to the claimants. This was intended to compensate the claimants for the “wasted” costs of dealing with the fictitious authorities.
• Indemnity: The defendants (the clients) were not to be held liable for the costs specifically attributable to the Fictitious Authorities Issue. The court ensured that the clients did not bear the financial burden of their solicitors’ professional negligence.
• Interest: Post-judgment interest was set at the standard rate of 5.33% per annum, running from 6 March 2026.

The court declined to order the maximum possible costs, noting that the solicitors had eventually admitted the error and expressed remorse. However, the $180,000 figure reflected the substantial nature of the underlying claims ($900,000 in total across the suits) and the significant procedural disruption caused by the fictitious citations.

Why Does This Case Matter?

This case is a landmark in Singapore’s legal landscape as it is one of the first to directly address the consequences of “AI hallucinations” in court submissions. While the court did not need to find as a fact that GenAI was used, the reasoning provides a clear framework for how such incidents will be treated in the future. It establishes that the use of technology does not create a “new” duty but rather highlights the enduring importance of the existing duty to the court.

For practitioners, the significance lies in the court’s refusal to accept “delegation” as a defense. In modern practice, research is often outsourced to junior staff or automated tools. Tan Hai Peng Micheal makes it clear that the solicitor on record is the “gatekeeper” of the information presented to the judge. This “non-delegable duty” means that every citation must be physically or digitally verified against an official report or a recognized database like LawNet before it is filed. The court’s reliance on Iskandar bin Rahmat v Public Prosecutor [2021] 2 SLR 1151 reinforces that this is a “professional responsibility” that cannot be shirked.

The case also expands the reach of personal costs orders. By including Mr. Sidhu—an assisting solicitor not on record—the court has signaled that it will look past formal designations to identify the individuals actually responsible for wasted costs. This has significant implications for law firm management and the supervision of external consultants or “freelance” researchers.

Furthermore, the judgment places Singapore in alignment with other major common law jurisdictions, such as the UK (Ayinde) and Australia (Murray v Victoria [2025] FCA 731), in taking a strict stance against the citation of fictitious authorities. It underscores that the “administration of justice” is a fragile system that depends on the honesty and diligence of its officers. As S Mohan J noted, citing Attorney-General v Shahira Banu d/o Khaja Moinudeen [2024] 4 SLR 1324, the court must be able to rely on the fact that the law is as represented by counsel.

Finally, the case serves as a practical guide for the application of Order 21 Rule 6 of the ROC 2021. It demonstrates that the court will use its costs powers not just to compensate the winning party, but to regulate the conduct of the profession and maintain public confidence in the judiciary. The imposition of a $180,000 global costs order, combined with personal liability for the solicitors, is a potent deterrent against procedural shortcuts and the “blind reliance” on unverified technology.

Practice Pointers

• Mandatory Verification: Solicitors must personally verify the existence and accuracy of every case name and neutral citation in their submissions. Cross-referencing against LawNet or the Singapore Law Reports is essential.
• Supervision of Subordinates: When delegating research to paralegals or junior associates, senior solicitors must implement a robust “check-the-checker” system. The fact that a subordinate prepared the draft is no defense to a personal costs order.
• AI Disclosure and Caution: If GenAI tools are used for research, practitioners should treat the output as a starting point only. Every “hallucinated” fact or citation must be caught before filing. Firms should consider internal policies regarding the disclosure of AI use to the court.
• Duty to the Court vs. Duty to Client: The duty to the court is paramount. Citing a fictitious authority, even if done unintentionally to support a client’s case, is a breach of this primary duty and can lead to personal financial and disciplinary consequences.
• Assisting Solicitors’ Liability: Solicitors providing “behind-the-scenes” assistance should be aware that they are still “officers of the court” and can be subject to personal costs orders under the Legal Profession Act 1966.
• Prompt Correction: If an error in citation is discovered after filing, counsel should immediately inform the court and the opposing party. Transparency may mitigate the “Stage 3” assessment of whether a personal costs order is “just.”
• Record Keeping: Maintain a “Bundle of Authorities” for every major submission. If a case cannot be found in a physical or digital report, it should not be cited.

Subsequent Treatment

As a 2026 decision, Tan Hai Peng Micheal v Tan Cheong Joo [2026] SGHC 49 represents the current high-water mark for the Singapore High Court’s treatment of AI-related procedural misconduct. It follows and expands upon the principles laid down in Tajudin bin Gulam Rasul v Suriaya bte Haja Mohideen [2025] 5 SLR 518 and [2026] SGHC 16. The ratio regarding the non-delegable duty of verification is expected to be followed in all future cases involving fictitious citations, whether generated by AI or human error.

Legislation Referenced

• Legal Profession Act 1966 (2020 Rev Ed), s 2
• Moneylenders Act (Cap 188, 2010 Rev Ed)
• Rules of Court 2021, Order 21 Rule 6 (O 21 r 6)
• Rules of Court 2021, Order 21 Rule 2 (O 21 r 2)
• Rules of Court 2021, Order 21 Rule 3 (O 21 r 3)
• Rules of Court 2021, Order 1 Rule 3

Cases Cited

• Applied: Ridehalgh v Horsefield [1994] Ch 205
• Considered: Tajudin bin Gulam Rasul v Suriaya bte Haja Mohideen [2025] 5 SLR 518
• Considered: Ayinde v London Borough of Haringey [2025] 1 WLR 5147
• Referred to: [2025] SGHC 217 (First Judgment)
• Referred to: [2026] SGHC 16
• Referred to: [2025] SGHC 214
• Referred to: Attorney-General v Shahira Banu d/o Khaja Moinudeen [2024] 4 SLR 1324
• Referred to: Zhou Tong v Public Prosecutor [2010] 4 SLR 534
• Referred to: Iskandar bin Rahmat v Public Prosecutor [2021] 2 SLR 1151
• Referred to: Sheagar s/o T M Veloo v Belfield International (Hong Kong) Ltd [2014] 3 SLR 524
• Referred to: Murray (on behalf of the Wamba Wemba Native Title Claim Group) v Victoria [2025] FCA 731

Source Documents

• Original Judgment at eLitigation
• Judgment PDF (Archived)