Ne Bis In Idem Principle

The ne bis in idem principle is a fundamental legal guarantee that protects individuals from being prosecuted or punished more than once for the same offence. It is commonly referred to as the prohibition against double jeopardy. Under Article 4 of Protocol No. 7 to the European Convention on Human Rights (ECHR), once a person has been finally acquitted or convicted of a criminal offence, they cannot be tried or punished again for the same offence within the same State. This principle promotes legal certainty, fairness, and finality in criminal justice by preventing repeated prosecutions based on the same conduct.

The European Court of Human Rights (ECtHR) clarified the scope of the principle in Sergey Zolotukhin v Russia (2009). The Court held that the decisive question is whether the subsequent proceedings concern the same facts or facts that are substantially the same, rather than whether the legal classification of the offences differs. Consequently, States cannot avoid the protection of Article 4 of Protocol No. 7 simply by describing the same conduct under different legal labels.

However, the Court has also recognised that modern regulatory systems may legitimately employ both criminal and administrative sanctions for the same underlying conduct. In A and B v Norway (2016), the Grand Chamber held that parallel proceedings do not necessarily violate the ne bis in idem principle where they form part of an integrated enforcement system. The Court established the test of whether the proceedings are sufficiently closely connected in substance and in time. Factors relevant to this assessment include whether the proceedings pursue complementary purposes, whether there is coordination between the authorities, whether evidence is shared to avoid duplication, whether the overall sanctions are proportionate, and whether the proceedings occur within a reasonably close timeframe.

In Jesus Pinhal v Portugal [2026], the applicant argued that the criminal proceedings, the proceedings before the Securities Market Commission (CMVM), and those before the Bank of Portugal amounted to being prosecuted three times for the same conduct. The ECtHR rejected this argument. It found that although the three proceedings arose from the same underlying events, they pursued different regulatory objectives: the criminal proceedings punished market manipulation; the CMVM proceedings protected investor confidence and the transparency of financial markets; and the Bank of Portugal proceedings safeguarded the stability of the banking system through prudential supervision.

The Court also emphasised that the three authorities worked in close cooperation. They exchanged evidence, coordinated their investigations from an early stage, relied on substantially the same documentary material, and conducted proceedings that progressed in parallel. As a result, the ECtHR concluded that the proceedings were sufficiently connected in substance and in time to form a coherent and integrated response to the applicant's misconduct. Therefore, despite the existence of multiple sanctions, there was no violation of Article 4 of Protocol No. 7, because the applicant had not been subjected to impermissible duplicate proceedings but rather to complementary proceedings within a single, coordinated enforcement framework.