UK Supreme Court clarifies standard of proof in extradition cases involving ECHR rights

Citation: [2023] UKSC 39
Judgment on


The case of Popoviciu v Curtea De Apel Bucharest (Romania) marks a significant development in UK extradition law and the application of the European Convention on Human Rights (ECHR) in “conviction extradition cases.” This analysis dissects the legal reasoning applied by the UK Supreme Court (UKSC) in its deliberations on whether the extradition of Mr. Gabriel Popoviciu to Romania would violate his ECHR rights due to an alleged flagrantly unfair trial. The key issues revolved around the appropriate standard of proof for establishing past violations of fair trial rights under Article 6 ECHR and the assessment of future risks related to extradition.

Key Facts

Mr. Popoviciu was indicted in Romania for implicated offenses concerning corruption and abuse of office, leading to a trial presided over by Judge Tudoran, who was later accused of corruption and having an undisclosed affiliation with a crucial prosecution witness. The European Arrest Warrant against Mr. Popoviciu prompted extradition proceedings in the UK, which culminated in challenges based on alleged unfair trial practices in Romania violating Articles 5 and 6 ECHR.

The central legal question was whether Mr. Popoviciu needed to substantiate ‘a real risk’ of a flagrantly unfair trial (a forward-looking assessment) or prove past trial unfairness on ‘the balance of probabilities’ (the civil standard of proof). The UKSC made a crucial distinction between proving past events (requiring balance of probabilities) and predicting future risks, which invoked the ‘real risk’ standard.

The Soering Principle, foundational in extradition law, was invoked, emphasizing that the responsibility of an extraditing state under the Convention may arise if substantial grounds are presented for the belief that the person, if extradited, would face a real risk of being subjected to treatment contrary to the ECHR.

However, an established exception in the context of evidence obtained by torture under Article 3 ECHR prompted the court to examine whether similar relaxation of standards should extend to allegations of judicial corruption.

The court also considered the availability in Romania of an effective legal procedure that would allow the respondent to argue the fairness of his trial and the legality of his detention, should he be extradited, in compliance with Article 5 ECHR requirements for lawful detention following a conviction.


The UKSC concluded that the High Court misapplied the legal standard by using the ‘real risk’ test associated with assessing future occurrences. Instead, the allegations of past trial unfairness needed to have been demonstrated on the balance of probabilities. As such, the UKSC found that the extradition appeal should not have succeeded on the ground that the High Court applied the incorrect standard.

Additionally, on the application of fresh evidence, the UKSC adhered to the stringent Fenyvesi criteria, determining that the fresh evidence sought to be adduced by the respondent did not meet the necessary threshold for it to influence the High Court’s decision.

Notwithstanding this, had the European Arrest Warrant not been withdrawn, the UKSC would have addressed the compelling argument regarding the lack of an effective remedy in Romania, remitting this issue back to the High Court for further consideration.


The UKSC judgment in Popoviciu v Curtea De Apel Bucharest demonstrates hitherto clarity in the standards of proof applicable in conviction extradition cases under the English law. It delineates the distinction between adjudicating past occurrences and assessing potential future risks, reinforcing the traditional approach underpinned by balance of probabilities in proving past events in conviction cases. The careful scrutiny given to the potential implications on ECHR rights underscores the UK’s commitment to protecting fundamental rights in the context of international judicial cooperation.

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