I. Introduction
In B.M. v. Switzerland (no. 50227/21, 12 May 2026), the European Court of Human Rights found a violation of Article 5 § 4 ECHR because the judicial review of the applicant’s continued preventive detention took place without an oral hearing. The applicant, a 75-year-old offender serving an indefinite measure of internment (internement) for sexual offences against pre-pubescent boys − including two of his stepsons − complained that the Zurich administrative tribunal had dismissed his release request without a hearing. The Chamber unanimously found no violation of Article 5 § 1, but held by five votes to two that the absence of an oral hearing rendered the review procedure incompatible with Article 5 § 4.
At first sight, the judgment appears to concern a familiar issue: the circumstances under which Article 5 § 4 requires an oral hearing in detention-review proceedings. Yet a closer reading suggests something more fundamental. In finding a violation, the Chamber relied on the applicant’s vulnerability, advanced age, personality assessment, and the absence of a recent judicial psychiatric evaluation − despite facts and procedural arrangements similar to those examined in Derungs v. Switzerland, where the Court had accepted the absence of an oral hearing.
This post argues that the real significance of B.M. lies neither in its treatment of oral hearings nor in its reliance on vulnerability as such. Rather, the judgment exposes the absence of a principled framework for addressing competing vulnerabilities under Article 5 § 4. While the Chamber relied on the applicant’s vulnerability to justify enhanced procedural protection, it offered little explanation as to why that vulnerability warranted a departure from Derungs − or how vulnerability should operate where multiple vulnerable interests coexist within the same provision.
II. B.M. v. Switzerland: The Court’s Reasoning under Article 5 § 4
The applicant had been subject to internment since 2005, following his 2003 conviction by the Zurich higher court for multiple sexual offences against pre-pubescent boys, with a diagnosis of exclusive-type paedophilia, classified under DSM-5 as a lifelong condition without a remission criterion. He consistently refused offence-oriented therapy. In October 2019, then aged seventy-three, he applied for conditional release. The application was rejected at every level and confirmed by the Federal Court on 24 March 2021, on the basis of an extensive risk assessment combining judicial and private psychiatric expertise, internal prison reports, and the applicant’s custody record.
On Article 5 § 1, the Court applied the D.J. v. Germany framework − developed in the context of the German “Sicherungsverwahrung” jurisprudence on preventive detention: continuing detention “after conviction” requires both that the refusal to release remain consistent with the original purposes of the measure and that it rest on a reasonable assessment in light of those purposes. The Chamber found both conditions satisfied. At § 95, citing N.Ç. v. Turkey, it emphasised that the legal interests at stake − the physical and moral integrity of children − were of heightened importance.
The procedural question was different. The Chamber reiterated that Article 5 § 4 does not require an oral hearing in every detention-review proceeding. Drawing on Waite v. United Kingdom and Ruiz Rivera v. Switzerland, it held that such a hearing is necessary where the judicial authority is to assess the personality and dangerousness of the person concerned (§ 102). The majority emphasised three considerations: the assessment of the applicant’s personality and the impact of his advanced age on future dangerousness; his vulnerability; and the absence of a recent judicial psychiatric assessment. The need for a hearing, the Chamber added at § 106, was “renforcée par sa situation de vulnérabilité et par l’absence d’une expertise légale récente”. Violation was found by five votes to two, with Judges Ranzoni and Grigoryan dissenting on this limb.
The Court’s conclusion is persuasive. Yet if these factors justified an oral hearing in B.M., how should that conclusion be reconciled with the earlier judgment in Derungs?
III. The Problem of Consistency: A Silent Departure from Derungs
The principal difficulty is not whether an oral hearing would have been desirable, but whether the Chamber adequately explained why one was required here but not in Derungs.
In Derungs v. Switzerland (2016), the applicant challenged the continued lawfulness of his preventive detention and expressly requested a hearing before the Zurich administrative tribunal. That request was rejected, the domestic court relying on earlier reports and noting that the applicant had been heard during the administrative phase. The Strasbourg Court accepted that approach and found no violation. Derungs was a deliberate doctrinal move: it distinguished Ruiz Rivera by reference to its specific circumstances, and it applied the Waite criterion − the necessity of an oral hearing where the court assesses personality and dangerousness − to conclude that, in preventive detention review, no additional clarification could reasonably be expected from a tribunal hearing.
The similarities are difficult to ignore. Both concerned preventive detention; both involved the review of future dangerousness; both relied on existing psychiatric and institutional assessments; and in both, the applicants had been heard during earlier stages. The majority in B.M. referred to the applicant’s advanced age, vulnerability, and the absence of a recent judicial psychiatric assessment as distinguishing features, yet stopped short of explaining whether these elements merely informed the overall assessment or constituted the decisive grounds for distinguishing Derungs. The earlier judgment is recognised as applicable (§ 101), but its substantive conclusion − that the Waite criterion can be met without a tribunal hearing in such proceedings − is set aside in silence. The dissenting opinion of Judges Ranzoni and Grigoryan exposes this gap clearly: the present case is “comparable, voire identique” to Derungs, and the majority “n’examine pas de manière suffisante l’affaire Derungs et ne dit rien qui permettrait d’expliquer pourquoi elle apprécie différemment la présente affaire”. The chronological priority of Waite and Ruiz Rivera over Derungs is, they note, “totalement négligé, voire passé sous silence”. The result is uncertainty as to the precise ratio of the decision.
This uncertainty matters for the predictability of the case-law and for the discipline of doctrinal evolution. Interpretive consistency is not a peripheral concern but a condition of the Court’s legitimacy: jurisprudential shifts must be reasoned, not merely performed (on the Court’s interpretive methods, see George Letsas). The need for such consistency is particularly acute given that the Court’s preventive detention jurisprudence − encompassing the Swiss internement regime, the German Sicherungsverwahrung line, and parallel mechanisms across European jurisdictions (see Jehle and others) − depends on doctrinal coherence for its application across systems. The apparent departure from Derungs points to a deeper question concerning the role of vulnerability in detention-review proceedings.
IV. Vulnerability as a Procedural-Rights Enhancer
A striking aspect of B.M. is the function assigned to vulnerability within the Chamber’s reasoning. The judgment treats it as a factor supporting enhanced procedural protection, yet offers little guidance as to its source or legal significance. It remains unclear whether the applicant’s vulnerability stemmed from his age, the length of his detention, his personal circumstances, or a combination. Vulnerability is invoked, but not theorised.
This is not an isolated development. Across Convention jurisprudence − notably under Article 3, in cases such as M.S.S. v. Belgium and Greece and Tarakhel v. Switzerland, and as analysed by Lourdes Peroni and Alexandra Timmer − vulnerability operates as a rights-enhancing concept, justifying heightened procedural obligations, intensified scrutiny, and stronger positive obligations. It has evolved from descriptive label into normative tool, connecting to what Corina Heri describes as the Convention’s responsiveness − its capacity to register the situated experience of the rights-holder. B.M. extends that logic into Article 5 § 4 detention-review proceedings: where a detainee is considered vulnerable, procedural guarantees may require reinforcement even where earlier case-law would not have pointed to the same conclusion. The development is consistent with broader trends in the Court’s vulnerability jurisprudence.
The difficulty, however, is that vulnerability does not exist in a vacuum. For a concept already under sustained critique for indeterminacy − Peroni and Timmer have warned of essentialising risks, and a more recent intervention by Timmer and others has restated that vulnerability remains both promising and contested − the absence of analytical specification matters. To be sure, the desirability of conceptual precision is itself contested. As Heri notes, the Court’s former Deputy Registrar Michael O’Boyle has argued that the vagueness surrounding vulnerability is intentional, avoiding the “straitjacket of definition” in order to preserve flexibility – a position from which Heri herself takes her distance, observing that such deliberate vagueness undermines the predictability and transparency of the case-law. Once vulnerability becomes a factor capable of expanding procedural rights, questions inevitably arise about its relationship with other vulnerable interests implicated by the same case. It is precisely here that B.M. becomes significant.
V. Whose Vulnerability Counts?
B.M. is best understood not as a case about vulnerability, but as a case about competing vulnerabilities.
The applicant’s vulnerability as an ageing detainee was not the only vulnerability present. The detention measure existed precisely because of the risk he posed to children − a group repeatedly recognised by the Court as among the most vulnerable under the Convention. In its Article 5 § 1 analysis, the Chamber accepted the importance of protecting children from future sexual victimisation. At § 95, citing N.Ç. v. Turkey, the Court reasoned that the legal interests at stake “sont d’une importance élevée puisqu’il s’agit de l’intégrité physique et morale d’enfants qui sont des personnes vulnérables”, and that internment was the only adequate response to the risk of reoffending.
Yet under Article 5 § 4, this dimension largely disappeared. The applicant’s vulnerability became a factor supporting enhanced procedural protection, while the vulnerability of the children whom the measure was designed to protect played no visible role in the analysis. It was not weighed against the applicant’s vulnerability. It was not even named.
If vulnerability is invoked as a reason for strengthening procedural guarantees, the Chamber must explain why one form of vulnerability becomes legally significant while another remains absent from the analysis. The difficulty is not that the Court recognised the applicant’s vulnerability − it is that the judgment offers no principled account of why that vulnerability acquired decisive procedural significance while the vulnerability of children at risk of future victimisation played no discernible role in the Court’s reasoning.
The omission is particularly striking because vulnerability appears to operate one-directionally: it functions as a justification for expanding procedural protection, but not as a consideration requiring reflection on situations involving multiple vulnerable interests. Such situations are likely to become more frequent. Cases concerning detention, child protection, migration, mental health, and domestic violence regularly involve several vulnerable actors whose interests cannot be considered in isolation − as the Court has acknowledged in Volodina v. Russia and Kurt v. Austria, where the vulnerability of victims structured the analysis of protective obligations. Moreover, vulnerability is not invariably rights-enhancing. It may also be instrumentalised to justify restrictions on rights or paternalistic interventions, illustrating the need for greater conceptual clarity regarding the functions vulnerability performs in Convention adjudication.
From this perspective, the most significant contribution of B.M. may not be its reaffirmation of oral hearings under Article 5 § 4. Rather, it is the question that the judgment leaves unanswered: once vulnerability becomes a rights-enhancing concept, what principles determine whose vulnerability counts, and why?
VI. Conclusion
B.M. v. Switzerland will be remembered as an important Article 5 § 4 judgment on oral hearings in detention-review proceedings. Yet its broader significance lies elsewhere.
The judgment departs from Derungs without explaining why the applicant’s vulnerability, advanced age, and the absence of a recent judicial psychiatric assessment justified a different procedural outcome. The dissenting opinion of Judges Ranzoni and Grigoryan exposes that silence with particular clarity. More importantly, B.M. illustrates a broader conceptual difficulty in the Court’s vulnerability jurisprudence. Vulnerability increasingly operates as a justification for enhanced procedural protection, yet the Court has not developed a coherent framework for situations in which multiple vulnerabilities coexist.
B.M. v. Switzerland may be remembered less for what it said about oral hearings than for what it failed to say about competing vulnerabilities. Until the Court develops a clearer methodology, questions of procedural fairness under Article 5 § 4 will remain intertwined with a broader challenge: the conceptual coherence of vulnerability as a category of Convention adjudication.
