Inter Partes Discovery under O.31 r.12 confined to opposing parties: notice parties in private law must use non‑party discovery (O.31 r.29)

Case: O’Sullivan & Anor v Allied Irish Bank plc & Anor; Everyday Finance DAC v O’Sullivan & Ors [2025] IEHC 487 (High Court, Kennedy J, 12 September 2025)

Introduction

This decision addresses a recurring and practically important question in Irish civil procedure: can a notice party in private law proceedings avail of inter partes discovery under Order 31 rule 12 of the Rules of the Superior Courts (RSC), or must it proceed (if at all) via non-party discovery under Order 31 rule 29?

Against the backdrop of a property development financing dispute, the plaintiffs (Michael and Mary O’Sullivan) sue their original lender AIB and its assignee Everyday Finance DAC alleging that, under a 2014 restructuring agreement, AIB was obliged to release mortgage charges over 14 units—four of which remain charged (the “Four Units”). Cottonlane Ltd, the purchaser and registered owner of the units, was joined as a notice party to the plaintiffs’ plenary proceedings (the “Substantive Proceedings”). Separately, Everyday counterclaims against the O’Sullivans and Cottonlane seeking, inter alia, to set aside the transfer of the Four Units (the “Counterclaim”).

The key procedural issue: Cottonlane, as notice party (and as a defendant to the Counterclaim), sought discovery under O.31 r.12 from the plaintiffs and from AIB. The Court had to decide whether Cottonlane could use inter partes discovery in these circumstances, or whether it must instead pursue non-party discovery under O.31 r.29. Ancillary issues arose about discovery sought for collateral proceedings, the independence of counterclaims, and the proper measure of relevance, necessity, and proportionality.

Summary of the Judgment

No inter partes discovery for notice parties in private law: Cottonlane, as a notice party in the Substantive Proceedings, is not entitled to inter partes discovery under O.31 r.12 because no claim is made by or against it in those proceedings and it is not litigating an issue inter se with the parties from whom discovery is sought (paras 2, 31–37, 45–51).
Counterclaim is independent: Although Cottonlane is a defendant to the Counterclaim, AIB is not. Discovery from AIB in the Counterclaim context can only be sought via O.31 r.29 (non-party discovery), after other routes are exhausted (paras 3, 18–19, 28–31).
Discovery cannot be sought for separate litigation: Cottonlane’s stated intention to use discovery in separate “Solicitors’ Proceedings” is an abuse. Discovery obtained is subject to an implied undertaking limiting its use to the proceedings in which it is obtained (para 26).
Even if jurisdiction existed, the application fails on the merits: Cottonlane did not satisfy the relevance, necessity, and proportionality thresholds. The parties whose pleadings defined the issues had already settled discovery parameters; Cottonlane was offered (conditional) access to that discovery and did not avail of it; and its categories and reasons veered into impermissible “fishing” (paras 5, 10–16, 48–49).
Manatee not followed: The Court declined to adopt the broader English approach in Manatee Towing v Oceanbulk allowing discovery between non-opposing parties. Irish r.12 retains the traditional “opposing party” focus reflected in authorities like Brown v Watkins and Shaw v Smith (paras 23–24, 51–53).
Path forward: Cottonlane may in future pursue non-party discovery under r.29 in the Counterclaim or in the Solicitors’ Proceedings, provided it exhausts inter partes discovery first and meets r.29’s stringent requirements (paras 6, 54).

Analysis

The new principle distilled

The High Court clarifies and reaffirms that inter partes discovery under O.31 r.12 is confined to opposing parties who are litigating an issue against each other as defined by their pleadings. A notice party in private law proceedings—unlike in public law judicial review—does not thereby gain plenary party status for discovery purposes. If a notice party needs documents from a party with whom it has no pleaded controversy in the relevant action, the correct route is non-party discovery under O.31 r.29, subject to the usual thresholds and the exhaustion requirement.

Precedents and authorities considered

1) Status of counterclaims as independent actions

Statute of Limitations Act 1957, s.6: Treats counterclaims as separate actions (para 18(a)).
Order 19 RSC framework for counterclaims: r.2 (trial together unless inconvenient), r.10 (adding non-plaintiff counterclaim defendants), r.15 (counterclaim can proceed if the original claim is discontinued/dismissed) (para 18(b)).
Claddagh Jewellers Ltd [2020] IEHC 325: Practical demonstration of the independence of claims and counterclaims (para 18(c)).
O’Donoghue v Martin [2019] IEHC 598: Pilkington J, drawing on Delany & McGrath, confirms counterclaims are separate and distinct, potentially against persons not parties to the original action (paras 18(d)–(e)).

2) Notice parties—public vs private law roles

Spin Communications v IRTC [2000] IESC 56, and BUPA v HIA [2005] IESC 80; [2006] 1 IR 201: “Vital interest” test for joinder in public law; notice parties may play a full role, often mirroring respondents (paras 20–21, 37).
Ballyboden Tidy Towns v An Bord Pleanála [2024] IESC 4: Confirms robust participation rights for notice parties in JR, including where the decision-maker concedes; they can continue to defend the decision due to their direct, vital interest (para 21).
Charles Kelly Ltd v Ulster Bank [2019] IEHC 711; Barlow v Fanning [2002] 2 IR 593; YAP v Temple Street [2006] IEHC 308; Dowling v Minister for Finance [2013] IESC 58: Joinder principles and the distinction between private and public law contexts—parties choose whom they sue in private law; the Court will rarely impose additional parties absent necessity to adjudicate all issues (paras 20, 34, 40, 44).

3) Discovery—adversarial character and thresholds

Peruvian Guano [1882] 11 QBD 55; Lyell v Kennedy (1883) 8 App Cas 217: Discovery and interrogatories are traditionally anchored in enabling a party to advance its case or damage its adversary’s case—between opponents (para 22).
Dome Telecom v Eircom [2007] IESC 59; Astrazeneca AB v Pinewood [2011] IEHC 159; Tobin v Minister for Defence [2019] IESC 57; Ryan v Dengrove DAC [2022] IECA 155: Proportionality and necessity—scope must be commensurate with its likely utility vis-à-vis the opponent’s case (para 22).
Chambers v Times Newspapers [1999] 2 IR 424: Non-party discovery principles—necessity, relevance, proportionality, and non-availability by other means (para 6).
Fitzwilton v Mahon (HC, 16 Feb 2006): No difference in principle in discovery between plenary and JR; in practice, JR needs less discovery (para 49).
Roussel v Farchepro [1999] 3 IR 567: Implied undertaking not to use discovered documents in other proceedings absent leave (para 26).
Sheehy & McAuley v Government of Ireland (HC, 30 July 2002); Swords v Western Proteins [2000] 1 IR 324: Parties cannot materially shift the basis/categories between voluntary requests and motions; applications must align with pleadings and initial requests (para 29).
Allied Irish Banks plc v Ernst & Whinney [1993] 1 IR 375: Illustration of non-party discovery (not “notice party” in the ongoing action)—helps distinguish terminology; what is often called “notice party discovery” in that context is, in substance, non-party discovery (para 16(a) n.1).

4) Co-defendant discovery and the “opposite party” requirement

Brown v Watkins (1886) 16 QBD 125; Shaw v Smith (1887) 18 QBD 183: “Any other party” in discovery rules means the opposite party; co-defendant discovery requires a “right to be adjusted” between them on an issue in dispute (paras 23, 50).
Manatee Towing v Oceanbulk [1999] CLC 1197: English High Court allowed discovery between non-opposing parties where necessary for fair disposal; but justified by different English rule wording and imminent CPR reforms; Kennedy J declines to follow it in Ireland given unchanged Irish r.12 wording and settled interpretation (paras 24, 51–53).

Legal reasoning

(1) Discovery must be anchored in a pleaded dispute between opponents

Order 31 r.12 allows “any party” to seek discovery from “any other party” of documents “relating to any matter in question” in the cause. Kennedy J interprets this in its traditional adversarial sense: the entitlement is between parties actually litigating an issue against each other as defined by their pleadings (paras 22, 45–47). This is reinforced by the equitable origins of discovery, the Peruvian Guano test (advance your case/damage your adversary), and the language used by Irish appellate courts in articulating necessity and proportionality (para 47).

(2) Notice parties in private law are not “full combatants” by default

Unlike in judicial review, where notice parties often defend a decision directly affecting them, a notice party in private law does not thereby gain the right to litigate substantive issues to which it is a stranger (paras 37–39). Here, the substantive dispute—what AIB agreed in 2014—is between the O’Sullivans and AIB. Cottonlane, lacking privity to that agreement and having served no pleadings in the Substantive Proceedings, does not become an “opponent” for r.12 purposes. Its interest is, at most, in consequential relief that may affect its title. That indirect interest does not ground inter partes discovery on the primary contractual issue (paras 36, 41–45).

(3) Counterclaims are independent actions: parties to one are not automatically parties to another

Because AIB is not a party to Everyday’s Counterclaim, Cottonlane cannot obtain inter partes discovery from AIB in the Counterclaim. If materials are needed from AIB for the Counterclaim, the route is non-party discovery under r.29, after exhausting inter partes discovery between the actual parties to the Counterclaim (paras 3, 28–31).

(4) The Court declines to follow Manatee

Although Manatee permitted discovery from a co-party where no live issue was joined between them, Kennedy J prefers the classic approach in Brown and Shaw, aligned to the unchanged Irish wording in r.12 and the Irish jurisprudence emphasising opponent-focused discovery. Even if Manatee’s broader jurisdiction existed in Ireland, this would be a rare case for exercising it, and the Court would not do so on these facts (paras 51–53).

(5) Collateral use is prohibited

Discovery sought expressly for use in separate “Solicitors’ Proceedings” is an abuse of process, given the implied undertaking limiting use of discovered documents to the proceedings in which they are produced. The correct route would be: obtain discovery in this action (if properly available), then seek the Court’s leave to use it elsewhere if necessary (para 26).

(6) Necessity, proportionality, and availability by other means

Even apart from the threshold defects, Cottonlane’s application failed the necessity and proportionality tests. The plaintiffs and AIB had already defined their discovery between themselves. AIB had offered Cottonlane conditional access to the discovery it was giving; Cottonlane neither availed of nor explained why that was insufficient—undercutting “necessity,” especially for any later r.29 attempt (paras 5–6, 48–49, 54). The categories were broad and inadequately tied to pleaded issues, amounting to “fishing” (paras 15(b), 16(f)).

Impact and practical significance

1) Clarity on discovery rights of notice parties in private law

This is a strong restatement—and in practice a clarifying development—of Irish discovery law: in private law plenary actions a notice party does not, by virtue of joinder, acquire inter partes discovery rights under O.31 r.12 where it is not litigating a pleaded issue against the target of discovery. This closes off a route sometimes assumed available in complex multi-party proceedings and aligns practice with the text and purposes of O.31 r.12.

2) Strategy for complex proceedings involving claims, counterclaims, and third-party interests

Define roles at joinder: Parties seeking to join supportive or affected entities in private law proceedings should consider whether those entities need to be joined as true parties (plaintiff/defendant) with pleadings, rather than as notice parties, if they are to seek discovery or litigate primary issues.
Use r.29 when appropriate: If documents are needed from a non-party to the relevant claim or counterclaim, prepare for r.29’s strict criteria: specificity, clear linkage to pleaded issues, necessity, proportionality, and non-availability by other means.
Exhaust inter partes discovery first: As emphasised, r.29 relief will “seldom be appropriate” unless inter partes discovery routes have been attempted and demonstrably failed or proved insufficient (paras 6, 54).
Align requests with pleadings: Voluntary requests and motions must be consistent and mapped to the relevant pleadings. Shifting grounds or categories without explanation risks refusal (paras 29–30).
Collateral use warning: Requests anchored in the needs of other proceedings are liable to be refused as an abuse. Seek leave for collateral use only after proper discovery is obtained in the present action (para 26).
Conditional access matters: Offers to share existing discovery, even conditionally, may undercut “necessity,” especially for r.29. Applicants should engage with such offers and be prepared to justify any residual need.

3) Limited utility of English Manatee line

Irish practitioners should not rely on Manatee to obtain discovery from co-parties with whom they are not in dispute. Unless and until r.12 is amended, the Brown/Shaw approach governs: “any other party” is essentially the opposing party for the issue in question.

4) Reinforcement of proportionality in discovery

This decision sits comfortably with the Supreme Court’s and Court of Appeal’s proportionality line. Courts will look for a tight connection between categories sought and pleaded issues, and for a realistic justification that discovery will materially advance or undermine a party’s case in relation to an opponent.

Complex Concepts Simplified

Inter partes discovery (O.31 r.12): Discovery between parties who are opponents on a pleaded issue in the same action (e.g., plaintiff vs defendant). The requesting party must show relevance and necessity to the “matter in question” between them.
Non-party discovery (O.31 r.29): Discovery from someone who is not a party to the relevant claim/counterclaim. It is exceptional and requires strict proof of relevance, necessity, proportionality, and lack of alternative means (e.g., cannot be obtained via inter partes discovery).
Notice party (private law): A person joined because they may be affected by the outcome, but who is not asserting or defending a claim in the action. In private law, notice party status does not generally confer full party rights for discovery on issues to which they are strangers.
Counterclaim independence: A counterclaim is a separate action within the same proceedings. Parties to the counterclaim are not automatically parties to the main claim. Discovery must respect that separation.
“Opposite party” and “right to be adjusted”: Classic English authorities (followed here) require that discovery be between parties who are adverse to each other on a live issue (“right to be adjusted”)—not merely co-parties with an interest in the overall outcome.
Fishing expedition: A request that is broad, speculative, or untethered to issues in the pleadings. Courts refuse such discovery to prevent undue burden and cost.
Implied undertaking: Documents obtained on discovery may be used only for the proceedings in which they are disclosed unless the Court grants permission to use them elsewhere.
Proportionality: The burden/cost of discovery should be proportionate to its likely value in advancing the case or undermining the opponent’s case.
Collateral use/abuse: Seeking discovery in one case for use in another is improper. Proper practice: obtain discovery for the present case and then apply for leave for collateral use if warranted.

Conclusion

Kennedy J’s judgment delivers a clear procedural message: in private law plenary proceedings, inter partes discovery under O.31 r.12 remains the province of opposing parties on pleaded issues. A notice party does not, by mere joinder, acquire discovery rights in disputes to which it is a stranger. Where documents are required from a non-party to the relevant claim or counterclaim, the proper route is O.31 r.29—and only after inter partes avenues are exhausted and the strict r.29 criteria are met.

The Court declines to extend Irish practice along the lines suggested by the English decision in Manatee. Instead, it aligns with classical authority (Brown v Watkins; Shaw v Smith) and with Irish jurisprudence on relevance, necessity, and proportionality. The judgment also underscores the independence of counterclaims, the inadmissibility of collateral use, and the practical importance of engaging with offers of conditional access to discovery.

Key takeaways for litigants and advisers:

Define clearly at joinder stage what role a non-primary participant is to play; notice party status in private law does not equate to full party rights.
Tie any discovery request tightly to pleaded issues against the opponent from whom discovery is sought.
Do not seek discovery for use in other proceedings; respect the implied undertaking.
Exhaust inter partes discovery before moving under r.29 and engage with any offers of access—necessity is judged in that context.
Expect courts to police proportionality rigorously and to refuse “general trawls.”

By reasserting these principles, the High Court provides welcome clarity on the rights and limits of notice parties in private law litigation and on the proper architecture of discovery when claims and counterclaims intersect.