Derivative Use of Lawfully Obtained Digital Evidence in Garda Disciplinary Proceedings: Commentary on Hyland v Commissioner of An Garda Síochána [2025] IESC 54

Derivative Use of Lawfully Obtained Digital Evidence in Garda Disciplinary Proceedings:
Commentary on Hyland v The Commissioner of An Garda Síochána [2025] IESC 54

1. Introduction

This commentary examines the Supreme Court of Ireland’s ruling in Patrick Hyland v The Commissioner of An Garda Síochána ([2025] IESC 54), delivered electronically on 12 December 2025. This ruling does not restate the Court’s full substantive reasoning on the legality of using material from a Garda member’s mobile phone in disciplinary proceedings; that reasoning is contained in the earlier substantive judgment of Murray J in [2025] IESC 43, in which O’Donnell C.J. and Dunne J. agreed and Hogan and Woulfe JJ. dissented.

Instead, [2025] IESC 54 addresses two practical but legally important questions that arise after the substantive decision:

  • The precise form of the order to be made by the Supreme Court, including whether it should grant an express declaration on the “derivative” or “indirect” use of information obtained from the applicant’s phone; and
  • The disposition of costs across the High Court, Court of Appeal and Supreme Court, and the consequences of the earlier High Court orders regarding the physical phone itself.

Although formally a ruling on order and costs, this decision consolidates and clarifies several important principles:

  • The limits of declaratory relief when a judgment already states the governing legal position;
  • The boundary between the Supreme Court’s appellate role and first‑instance fact‑finding, especially regarding technical issues around digital devices;
  • The interaction between criminal investigations, Garda disciplinary processes, property rights and the handling of potentially unlawful digital material; and
  • The developing approach to costs in complex, public‑law‑laden litigation, particularly following Little v Chief Appeals Officer [2024] IESC 53.

To understand the significance of [2025] IESC 54, it is necessary to situate it briefly within the wider litigation history.

1.1 Background in Outline

The applicant, Patrick Hyland, is (or was) a member of An Garda Síochána. His mobile phone was seized under a search warrant issued in the course of a criminal investigation. Material discovered on that phone led not only to the criminal investigation, but also to disciplinary investigations within An Garda Síochána, including investigations commenced by Superintendents Costello (30 August 2019) and Creighton (17 July 2020.

Hyland challenged:

  • The use of material from his phone in disciplinary proceedings;
  • The retention of his phone by the Commissioner after the conclusion of the criminal investigation; and
  • The onward “utilisation” of material obtained under a criminal search warrant for non‑criminal (disciplinary) purposes.

As the proceedings developed, the focus narrowed to the second of the two disciplinary investigations (the “Creighton” investigation). The litigation travelled through three levels:

  1. High Court (Barr J.): Partial success for the applicant and important declarations on retention and return of property, and disciplinary use of seized material.
  2. Court of Appeal: The applicant successfully appealed part of the High Court’s decision, obtaining a ruling that the material uncovered on his phone could not itself be directly used in the disciplinary proceedings, while the Court of Appeal left open the question of “indirect” or “derivative” use.
  3. Supreme Court – Substantive judgment [2025] IESC 43: The Commissioner, but not the applicant, appealed to the Supreme Court. The Court held (in essence) that:
    • The Commissioner was not entitled to retain the phone for the purposes of disciplinary investigations (subject to ownership and lawfulness qualifications); and
    • While direct use of the downloaded or copied material from the device in disciplinary proceedings was impermissible, “derivative” or “indirect” use of lawfully acquired information could be permissible if lawful, proportionate and respectful of privacy rights.

The ruling in [2025] IESC 54 builds on and operationalises those conclusions by settling the form of order, dealing with the fate of the phone, and determining costs.

2. Summary of the Ruling in [2025] IESC 54

2.1 Issues Before the Court

The Court addresses three principal matters:
  1. Form of Order:
    • Whether the Supreme Court should grant a specific declaration in the terms sought by the Commissioner concerning the lawfulness of “derivative” or “indirect” use of information from the applicant’s phone in disciplinary investigations.
    • How to reflect the Court’s substantive conclusions in its formal order, especially in light of the Court of Appeal’s prior order and the standing High Court orders.
  2. Disposal of the Phone:
    • Whether the Supreme Court should itself make an order directing the return of the phone to the applicant, and if so on what conditions, considering the Commissioner’s concerns about material on the phone which may amount to child pornography.
  3. Costs:
    • How costs should be allocated across the High Court, the Court of Appeal and the Supreme Court, in light of both parties’ mixed success and the public importance of the legal issues, applying the principles from Little v Chief Appeals Officer [2024] IESC 53.

2.2 Core Outcomes

The Supreme Court concludes as follows:

  • No declaratory order in the terms sought by the Commissioner is granted. The Court states there is “no reason to reduce the finding in the case to a declaratory order” because “the judgment speaks for itself”.
  • The Court’s formal order records that:
    • The appeal from the decision of the Court of Appeal is allowed in part, insofar as the Court of Appeal did not address what it termed “derivative” or “indirect” use of information from the applicant’s phone, and that such derivative use is permissible in line with Murray J.’s judgment.
    • The stay on the two disciplinary investigations (Costello and Creighton) is lifted.
  • No fresh order is made regarding the return of the phone. The Supreme Court leaves undisturbed the second and third parts of Barr J.’s High Court order, which:
    • Forbid retention of property seized in a criminal investigation solely on the basis that it is relevant to a disciplinary investigation; and
    • Recognise a general entitlement to return of property at the conclusion of criminal proceedings, subject to:
      • the owner establishing ownership or right to possession of all material on the device; and
      • the procedure under s.1 of the Police (Property) Act 1897 (as amended) in the District Court.
  • The Court expressly notes that the Commissioner has never contended that the allegedly unlawful material on the phone is incapable of removal and accepts that the DPP has decided not to prosecute for possession of that material.
  • On costs, the Court:
    • Emphasises that the case raised novel and important issues of public and private law.
    • Notes that:
      • The applicant succeeded in part in the High Court (66% of costs had been awarded there);
      • He succeeded fully in the Court of Appeal (awarded all costs below); and
      • In the Supreme Court, neither side achieved a complete victory: the applicant did not secure an absolute bar on any use of the material, and the Commissioner did not secure the right to use downloaded or copied material in disciplinary proceedings.
    • Awards the applicant 50% of his costs in each court (High Court, Court of Appeal, Supreme Court).
  • The Court also notes and corrects a typographical error in Murray J.’s earlier judgment (footnote 5, “lawful” should be “unlawful”).

3. Detailed Analysis

3.1 Procedural Posture and the Scope of the Appeal

3.1.1 High Court (Barr J.)

In the High Court, the applicant originally sought:

  • Orders restraining both sets of disciplinary proceedings (Costello and Creighton investigations);
  • Orders for the return of his phone; and
  • Orders preventing the Commissioner from “utilising” materials obtained on foot of the criminal search warrants for non‑criminal purposes.

Ultimately, the case focused on the “Creighton” disciplinary investigation. Barr J. made three key declarations (summarised at para. 5 of the Supreme Court ruling):

  1. Use in disciplinary proceedings: A declaration that the Commissioner was entitled to use the material found by the Gardaí as a result of the execution of the search warrants in disciplinary investigations concerning the applicant.
  2. No retention solely for disciplinary relevance: A declaration that:
    “the Respondent is not entitled to retain property seized during a search conducted as part of a criminal investigation after the conclusion of that investigation on the grounds that such material would be of relevance to an ongoing disciplinary investigation against the Garda who owns the property.”
  3. General right to return of property, with digital‑device proviso: A declaration that:
    “in general a person is entitled to return of their property once criminal proceedings have been concluded subject to the proviso that where material is on a computer or a mobile phone the applicant must be in a position to establish ownership or at least a right to possession of all the material on the computer or phone prior to it being returned to them any application for return of property seized in this case can be made to the District Court in the ordinary way pursuant to s. 1 of the Police Property Act 1897 (as amended).”

The applicant appealed only part of this order: specifically, the first declaration concerning use of material in disciplinary proceedings. He did not appeal the second and third declarations concerning retention and return of property.

Importantly, the Commissioner:

  • Did not file a cross‑appeal; and
  • Indicated in the Respondent’s Notice that he did not intend to seek a variation or substitution of the High Court order (“Not applicable”).

This procedural posture is critical: it means that the High Court’s declarations on retention and return of the phone remained intact unless and until specifically appealed or varied. The Supreme Court later treats those orders as still operative.

3.1.2 Court of Appeal

In the Court of Appeal, the applicant succeeded. The Court of Appeal:

  • Held that the material uncovered on the phone could not itself be directly used in the disciplinary proceedings against him; but
  • Did not express a view on whether such material could be used in an “indirect” or “derivative” way.

The Court of Appeal made a relatively simple order, setting aside only the specific part of Barr J.’s order that permitted disciplinary use of the seized material, while explicitly leaving the remainder of the High Court order intact (including the retention and return of property declarations).

3.1.3 Supreme Court: Substantive Appeal and this Ruling

The Commissioner sought and obtained leave to appeal to the Supreme Court. The grounds of appeal were framed around a single central proposition (para. 9):

“The Court of Appeal erred in law in holding that it is not permissible for the Commissioner of An Garda Síochána to use material in disciplinary proceedings in respect of a member of An Garda Síochána where the material was found on the member’s mobile phone, in circumstances where the phone was seized pursuant to a search warrant issued in the course of a criminal investigation.”

No cross‑appeal or additional grounds were raised by the applicant at Supreme Court level. Thus, the Supreme Court’s task was, strictly speaking, confined to reviewing the correctness of the Court of Appeal’s ruling on the use of the material – not the retention and return of the phone itself.

Nonetheless, as Murray J. explained in [2025] IESC 43 (summarised at para. 10 of this ruling), it was impossible to address the use question without understanding:

  • (a) The law governing the retention of the phone; and
  • (b) The distinction between:
    • copies or downloads of material from the phone; and
    • information or knowledge obtained by Gardaí as a result of executing the warrant.

On those points, the Supreme Court (unanimously on this aspect) held:

  • The Commissioner was not entitled to retain the phone purely for the purposes of disciplinary investigations, subject to:
    • the applicant being the owner of the phone; and
    • the principle that a person is not entitled to insist on the return of material it is unlawful for them to possess.
  • The Court distinguished between:
    • Direct use of downloaded or copied material from the phone; and
    • Derivative or indirect use of the knowledge lawfully acquired from the phone’s contents.
    Direct use was held impermissible in the circumstances; derivative use was held permissible if lawful, proportionate, and respectful of the applicant’s rights.

The ruling in [2025] IESC 54 then addresses the consequential matters: what should the final order say, what happens to the phone, and how should costs be apportioned.

3.2 Refusal of the Additional Declaratory Order

The Commissioner asked the Supreme Court to make a declaration stating in effect that:

“In circumstances where, as a consequence of the lawful execution of a search warrant, the Commissioner has become aware that the Applicant's phone contains information, and that knowledge was acquired lawfully, it is permissible for the Commissioner (and others exercising a statutory obligation to whom the information is lawfully transmitted) to make derivative or indirect use of that information for the purposes of discharging their statutory obligations, so long as such use is lawful, not in breach of the Applicant's right to privacy and proportionate to the objective of enforcing Garda discipline.”

This proposed declaration is essentially a restatement of the principle already articulated in the substantive judgment of Murray J. The Supreme Court refuses this request for two main reasons (paras. 2–3):

  1. Redundancy: The Court considers there is “no reason to reduce the finding in the case to a declaratory order.” The principle is already clearly set out in the judgment; “the judgment speaks for itself.”
  2. Concession by the Commissioner: The Commissioner himself “acknowledges that a declaration is not necessary” (para. 3 of his submissions). Granting a declaration in those circumstances would have been gratuitous and potentially confusing.

From a doctrinal perspective, this is noteworthy:

  • It underscores the distinction between a judgment (which contains reasoning and statements of law) and a formal declaratory order (which is an operative part of the court’s order).
  • The Supreme Court is signalling that not every legal conclusion in a judgment needs to be “translated” into a formal declaration. Where the principle is clear, the judgment itself can guide future conduct and lower courts without a separate declaratory paragraph.
  • This avoids the risk that a formulaic declaration might inadvertently narrow, distort or ossify what is in fact a nuanced principle developed in the judgment.

Instead, the order explicitly records only that:

  • The appeal is allowed in part; and
  • The part allowed is specifically that the Court of Appeal did not address the permissibility of derivative or indirect use of information from the phone, which the Supreme Court holds to be permissible in accordance with Murray J.’s judgment.

The result is a clean, minimal order that:

  • Reverses the Court of Appeal only to the extent necessary; and
  • Leaves the substantive reasoning to be drawn from the judgment itself, not from a new, possibly over‑simplified declaratory formula.

3.3 Treatment of the Applicant’s Phone and Unlawful Material

3.3.1 Effect of the Existing High Court Orders

The applicant sought, before the Supreme Court, an order directing the return of his phone. The Commissioner responded that such an order was unnecessary, because:

  • Orders 2 and 3 of Barr J.’s judgment (on retention and return) were never appealed and therefore remain in place; and
  • The effect of those orders is already to require the return of the phone, subject to the provisos outlined above (ownership/right to possession of all material, and recourse to the District Court under the Police (Property) Act 1897).

The Supreme Court accepts this logic. Having stressed that the appeal before it concerned only the use of material, it is careful not to disturb unappealed aspects of the High Court order. This reflects a strong respect for procedural regularity:

  • Parties are expected to frame and pursue their challenges properly (via appeals, cross‑appeals, or notices to vary).
  • Absent such steps, orders made by lower courts stand and are not revisited at the appellate level.

3.3.2 The Commissioner’s Concerns about Unlawful Material

The Commissioner makes two key concessions or assertions (paras. 11–13):

  1. He has never argued that there is unlawful material on the phone which “cannot be removed” in a way that would prevent ever returning the phone.
  2. He now states that:
    • There is material on the phone that “may be considered to constitute child pornography” (i.e. material it is not lawful for the applicant to possess);
    • He is understandably concerned about returning the device while this material remains on it; and
    • Removing such material is not technically straightforward, and the details of the procedure and any disputes about lawfulness may need to be addressed in evidence before the High Court.

These submissions place the Supreme Court in a delicate position: it must respect both:

  • The public interest in ensuring that unlawful material (particularly material characterised as child pornography) is not returned to an individual; and
  • The applicant’s property rights and the existing legal framework (including the High Court orders and the Police (Property) Act procedure) governing the return of seized property after criminal proceedings conclude.

3.3.3 Entitlement, but Not Obligation, to Remove Unlawful Material

The Supreme Court recalls that its substantive judgment had envisaged that the Commissioner has an entitlement—but not an absolute obligation—to remove material believed to be unlawful from the phone before returning it (para. 14). In parallel:

  • The applicant has a clear interest in not asserting ownership over material the Commissioner contends is unlawful.

The Court hints that, given these complementary interests, the parties might reasonably be expected to agree on a practical method for dealing with the device so that:

  • Unlawful material is not returned; and
  • The applicant’s lawful property interest in the device (and lawfully possessed data) is vindicated.

But crucially, the Supreme Court declines to design such a procedure itself.

3.3.4 Deferring Factual and Technical Issues to the Lower Courts

The Court adopts the first of the options suggested by the Commissioner: it makes no order regarding the return of the phone, and explicitly leaves:

  • The High Court orders to stand; and
  • Any further disputes about the phone to:
    • Negotiation between the parties; or
    • Proceedings in the District Court under s.1 of the Police (Property) Act 1897, or such other proceedings as the applicant may choose to bring.

The Court gives several reasons (para. 15):

  1. The relevant part of the High Court order has never been appealed; it therefore already governs the fate of the phone.
  2. The Commissioner has had “plenty of time” to address the phone, which further undercuts the need for the Supreme Court to intervene now.
  3. The issues the Commissioner wishes to ventilate (technical challenges in removing data; evidential disputes about whether particular material is unlawful; modalities of return) are “essentially factual matters” that could have been, but were not, brought before the Court in this appeal.

The Court concludes that it is “not appropriate” for the Supreme Court to open a new factual inquiry at this stage. This:

  • Reaffirms the Supreme Court’s role as a court of law, not fact, and its reluctance to become a case‑management or technical fact‑finding forum; and
  • Preserves the integrity of the appellate process by confining the Court to the record and issues as framed by the parties’ appeals and cross‑appeals.

3.4 Direct vs Derivative Use of Information

Although the ruling at [2025] IESC 54 does not re‑set out in full the Court’s substantive analysis on “derivative” use (which is contained in [2025] IESC 43), it clarifies the upshot:

  • The Court of Appeal had prohibited the direct use of the material seized from the phone in disciplinary proceedings, and had not decided the issue of indirect use.
  • The Supreme Court holds that:
    • Use of downloaded or copied material from the phone as such in disciplinary proceedings is not permissible in the way the Commissioner had contended; but
    • “Derivative” or “indirect” use of information lawfully obtained via execution of the warrant is permissible, provided:
      • the use is lawful;
      • it does not breach the applicant’s right to privacy; and
      • it is proportionate to the objective of enforcing Garda discipline.

In simplified terms, the Court draws a line between:

  • Using the actual digital artefacts extracted from the device (screenshots, downloaded files, etc.) in a new context (discipline), and
  • Acting on the knowledge that those artefacts provided: for example, using what was seen on the phone to:
    • identify witnesses;
    • frame questions in a disciplinary interview; or
    • conduct further lawful inquiries.

The Supreme Court clearly treats the latter as generally permissible, within the boundaries of lawfulness, proportionality and respect for privacy, while the former raises more serious concerns about repurposing data obtained under a criminal warrant.

This bifurcation is a crucial part of the new legal landscape for digital evidence:

  • It acknowledges that knowledge once lawfully acquired by the State cannot easily be “un‑known”; but
  • It also limits the reuse of seized digital material as such in new contexts, recognising privacy and data protection concerns, and the importance of ensuring that search warrants are not used as a back‑door route to obtain evidence for other proceedings beyond their authorised scope.

3.5 Costs and the Influence of Little v Chief Appeals Officer

On costs, the Court expressly applies the principles set out in Little v Chief Appeals Officer [2024] IESC 53 (para. 16).

Key features of the costs analysis are:

  1. Public importance and complexity: The case raised “novel and involved” issues of considerable importance, engaging significant questions of both public and private law, including:
    • The interaction of criminal investigation powers with disciplinary processes;
    • The handling of lawfully obtained digital evidence; and
    • The rights of Garda members as individuals vis‑à‑vis the disciplinary regime.
  2. Outcomes across the courts:
    • High Court: The applicant succeeded in part, and was awarded 66% of his costs.
    • Court of Appeal: The applicant succeeded entirely and was awarded all his costs in both courts.
    • Supreme Court: The outcome was mixed:
      • The applicant did not secure the “absolute order” he sought prohibiting any use of the material obtained from his phone; but
      • The Commissioner failed to establish that he could use downloaded or copied material from the phone in disciplinary proceedings.
  3. Resulting order: The Court concludes that the fair outcome is to award the applicant 50% of his costs in each court.

This approach reflects the post‑Little trend in Irish law towards a more context‑sensitive and outcome‑balanced treatment of costs in complex, rights‑oriented public law cases:

  • Success is no longer viewed in rigid “winner takes all” terms, especially where both sides contribute to the clarification of important legal issues.
  • The Court is mindful that the applicant’s litigation produced a measure of public benefit: clarifying the law on digital evidence, disciplinary use and property rights, even where he did not succeed in obtaining all the relief sought.
  • At the same time, it recognises that the Commissioner prevailed on the permissibility of derivative use, and that full indemnity of the applicant’s costs would not reflect the true balance of success and failure.

3.6 Correction of Typographical Error

Finally, the Court notes that there is a typographical error in footnote 5 of Murray J.’s substantive judgment: the word “lawful” should be “unlawful”. The Court orders that this be corrected and an amended version placed on courts.ie (para. 17).

While minor, this reflects the Court’s concern to ensure the clarity and precision of its published judgments, particularly where the correction concerns the key distinction between “lawful” and “unlawful” possession—central to the analysis of what material may or may not be returned to the applicant.

4. Precedents and Authorities Discussed

4.1 Little v Chief Appeals Officer [2024] IESC 53

Although the ruling does not summarise Little in detail, it cites it as setting out the “principles” governing costs in this type of litigation (para. 16).

In broad terms, Little stands for a more flexible, principled approach to costs in public law:

  • Costs should reflect not only who “won” in a narrow sense, but also:
    • the complexity and novelty of the issues;
    • the public importance of the questions decided;
    • the degree of success of each party; and
    • the conduct of the parties.
  • In appropriate cases, especially where important legal issues are clarified, the courts may depart from the traditional rule that “costs follow the event”.

Hyland is a textbook application of these principles:

  • Both parties contributed to clarifying the law on use of digital evidence in disciplinary processes.
  • Neither party obtained complete success.
  • The issues have system‑wide significance for Garda discipline and the handling of seized property.

The 50% costs order demonstrates how Little guides the Court away from all‑or‑nothing costs outcomes in complex cases involving mixed success and public interest elements.

4.2 Police (Property) Act 1897, s.1

The Police (Property) Act 1897 (as amended) provides a statutory framework for the disposal of property in the possession of the police (in Ireland, Garda Síochána) where no criminal proceedings are on foot, or after such proceedings have concluded. Section 1 empowers the District Court, upon application, to:

  • Order the disposal or return of property in Garda custody; and
  • Determine questions of ownership or right to possession where they are in dispute.

In this case, Barr J.’s order (left undisturbed by the Supreme Court) channels disputes about the applicant’s entitlement to the phone, and about the lawfulness of material on it, into Police Property Act proceedings in the District Court.

This has several implications:

  • The District Court, not the Supreme Court, is the proper forum to hear evidence about:
    • technical processes for removing alleged unlawful material;
    • the content of the phone; and
    • ownership and right to possession of data and device.
  • The statutory scheme offers a structured, fact‑sensitive mechanism for balancing:
    • the property rights of individuals;
    • the need to ensure that unlawful items (e.g. contraband, including child sexual abuse images) are not returned; and
    • the interests of justice in the disposal of seized items.

5. Simplifying Complex Legal Concepts

5.1 Judgment vs Order vs Declaration

  • Judgment: The written reasons of the court, setting out the facts, issues, legal principles, and reasoning. It often contains general statements of law.
  • Order: The formal, operative part of the court’s decision: what is actually ordered to happen (appeal allowed/dismissed, injunction granted, stay lifted, etc.).
  • Declaration: A specific type of order where the court formally states what the law is as between the parties (e.g. “It is declared that X is entitled to…” or “It is declared that Y is unlawful…”).

In Hyland, the Supreme Court decides that:

  • Its judgment already clearly states that derivative/indirect use of lawfully obtained information is permissible;
  • A separate declaratory order repeating this is unnecessary and might be redundant; and
  • The order need only record the key outcomes (partial allowance of appeal, lifting of stays, and costs).

5.2 Direct vs Derivative (Indirect) Use of Evidence

The Court distinguishes between:

  • Direct use:
    • Using the actual seized material (files, images, texts, screenshots) in disciplinary proceedings, essentially as evidence of misconduct.
  • Derivative or indirect use:
    • Using the knowledge gained from that material to guide further lawful action – for example:
      • Identifying people to interview;
      • Formulating lines of inquiry;
      • Drafting disciplinary charges that are then proved by independently gathered evidence.

The Supreme Court accepts that once the State has lawfully obtained information, it may usually act on that knowledge, but it restricts the re‑deployment of the actual digital artefacts from the criminal process into the disciplinary process.

5.3 Appeals, Cross‑Appeals and Notices to Vary

The case illustrates the importance of the technical architecture of appeals:

  • An appeal challenges parts of a lower court’s order that the appellant is dissatisfied with.
  • A cross‑appeal allows the respondent to challenge other aspects of the same order (which they might also consider wrong) without filing a separate appeal.
  • A notice to vary allows a respondent to maintain the lower court’s order but argue that it should be upheld on different grounds.

In Hyland:

  • The applicant appealed only the High Court’s declaration allowing disciplinary use of the material.
  • The Commissioner did not cross‑appeal or seek to vary the High Court’s orders on retention and return.

As a result, the Supreme Court:

  • Could properly reconsider the use of the material in disciplinary proceedings; but
  • Was not invited (and declined) to reopen the retention/return orders, which remain binding and must be worked out in the lower courts.

5.4 “Ownership or Right to Possession” of Digital Material

Barr J.’s order—and the Supreme Court’s acceptance of it—introduces a significant qualification for digital devices: before a phone or computer is returned, the applicant must establish ownership or right to possession of all material on the device.

This reflects the reality that:

  • A device can hold:
    • lawful personal data of the owner;
    • the personal data of others;
    • data downloaded or stored without the owner’s right to possess it (e.g. unlawful images); and
    • material that belongs to third parties (e.g. work product, confidential information).
  • The State cannot be ordered to hand back material it is unlawful for the person to possess.

Therefore, questions about which data may lawfully be returned, deleted, or retained will often require evidence and careful fact‑finding, rightly left to the District Court under the Police (Property) Act framework.

5.5 Mixed Outcome Costs in Public Law Litigation

Hyland shows how the courts now treat costs where:

  • The case raises systemic issues that go beyond the immediate interests of the parties;
  • The outcome is split: each party wins and loses on different issues; and
  • Both parties’ participation contributes to clarifying the law.

Rather than mechanically awarding costs to the “winner,” the Court:

  • Assesses the relative degree of success and failure; and
  • Strikes a balance (here, 50% costs to the applicant in each court), consistent with the principles in Little.

6. Impact and Future Significance

6.1 For Garda Disciplinary Practice

The combined effect of [2025] IESC 43 and [2025] IESC 54 is to set out a clear, structured framework for how An Garda Síochána may handle digital material seized in criminal investigations when disciplinary implications arise:

  • No indefinite retention purely for discipline:
    • The Commissioner cannot retain a Garda member’s phone after the conclusion of a criminal investigation merely because it contains material relevant to disciplinary proceedings.
  • Permissible derivative use:
    • Knowledge lawfully gained from the phone may be used indirectly in disciplinary processes, provided this use is lawful, respects privacy rights, and is proportionate.
  • Limits on direct reuse of seized digital material:
    • Using downloaded or copied material from the device as direct evidence in discipline is constrained and was not accepted in the broad way argued by the Commissioner.
  • Need for protocols on unlawful material:
    • Where devices contain potentially unlawful material (e.g. child sexual abuse images), An Garda Síochána will need clear, lawful procedures for:
      • Identifying such material;
      • Removing it where appropriate; and
      • Engaging with the District Court under the Police (Property) Act for any disputed returns.

6.2 For Privacy and Data Protection Law

The decision is also important in the broader context of data protection and privacy:

  • It recognises that data obtained under a criminal search warrant is not a free‑floating resource that the State can redeploy without limit in other contexts.
  • By prohibiting (in this context) direct use of downloaded material while permitting derivative use, the Court balances:
    • The State’s legitimate interest in maintaining discipline within An Garda Síochána; and
    • The privacy and data protection rights of individuals whose devices have been searched for specific criminal purposes.
  • The requirement that any derivative use be “lawful, not in breach of the applicant’s right to privacy and proportionate” encourages disciplinary bodies to:
    • Conduct a proportionality analysis before relying on information acquired from criminal search warrants;
    • Ensure that any further processing of such information complies with applicable data protection laws.

6.3 For Digital Evidence and Multi‑Purpose Use of Seized Material

Hyland will likely be cited in future cases involving:

  • Regulators or professional bodies seeking to use material obtained by the Gardaí or other investigators for non‑criminal purposes (disciplinary, regulatory, civil);
  • The distinction between:
    • using knowledge gleaned from a lawful search; and
    • reusing the physical/digital items obtained in that search as evidence in new proceedings.

Although the decision arises in the specific context of Garda discipline, its reasoning is likely to influence:

  • Other professional regulators (doctors, lawyers, accountants) who receive information from criminal investigations;
  • The development of policies on information‑sharing between agencies; and
  • The design of warrants and statutory powers authorising multi‑purpose or subsequent use of seized data.

6.4 For Litigation Strategy and Appellate Practice

The ruling sends clear signals to litigants and lawyers:

  • If a party wishes to challenge or defend parts of a lower court’s order (e.g. on retention or return of property), it is essential to:
    • file a cross‑appeal or notice to vary; and
    • ensure relevant factual issues (such as technical difficulties with digital forensics) are ventilated in the lower courts.
  • The Supreme Court will not readily:
    • reopen unappealed orders; or
    • conduct first‑instance factual inquiries on technical matters arising for the first time at the final appellate stage.

This will likely influence how future public law and disciplinary cases are framed and argued, encouraging more careful management of appeals and earlier presentation of relevant evidence.

6.5 For Costs in Public Interest and Public Law Litigation

Finally, the costs ruling contributes to the growing body of post‑Little jurisprudence on costs:

  • It confirms that where cases raise novel and important issues, a party who achieves only partial success may still be awarded a substantial portion of costs.
  • This may have a positive effect on access to justice, as litigants contemplating complex public law challenges can see that:
    • They will not automatically face a catastrophic costs order if they do not win outright; and
    • The courts recognise the public value in clarifying the law, even where outcomes are mixed.

7. Conclusion

Hyland v The Commissioner of An Garda Síochána [2025] IESC 54 completes the Supreme Court’s treatment of a challenging and sensitive case at the intersection of criminal investigation, Garda discipline, digital evidence, privacy rights and property law.

The ruling:

  • Reaffirms that the Court’s judgment, rather than a formal declaration, is the appropriate vehicle for articulating the new principle that derivative use of lawfully obtained information is permissible, subject to legality, privacy and proportionality;
  • Refuses to make fresh orders about the return of the phone, respecting the standing High Court orders and channelling factual and technical disputes into Police (Property) Act proceedings in the District Court;
  • Confirms that:
    • the Commissioner cannot retain a phone after a criminal investigation solely because of its disciplinary relevance;
    • direct use of downloaded or copied material from the device for discipline is not justified in the broad terms sought;
    • yet derivative or indirect use of information is permissible within structured legal limits;
  • Applies Little v Chief Appeals Officer to award the applicant 50% of his costs in each court, reflecting a nuanced, fairness‑based approach to costs in complex public law litigation.

Taken together with the substantive judgment in [2025] IESC 43, this ruling sets an important precedent for how Irish law will navigate the increasingly common scenario where digital evidence obtained under criminal powers has potential implications in parallel regulatory or disciplinary spheres. It balances, in a carefully structured way, the competing demands of:

  • Effective discipline within An Garda Síochána;
  • The rule of law and procedural fairness in appellate practice;
  • Individual privacy and property rights in the digital age; and
  • The public interest in ensuring that unlawful material is not returned to private citizens.

As such, Hyland is likely to become a leading authority on the derivative use of lawfully obtained digital information in disciplinary proceedings, and a key reference point for future cases at the interface of criminal law, administrative law and data protection.

Case Details

Year: 2025
Court: Supreme Court of Ireland

Comments