The so-called exception of res judicata, specifically contemplated in criminal proceedings as one of the articles of pre-judgment (art. 666.2 LECrim), is a direct consequence of the ne bis in idem principle, configured as a fundamental right contemplated in article 25.1 CE. The prohibition of incurring in this principle includes, in its procedural aspect, the prohibition of double criminal proceedings in which there is identity of subject, fact and basis; and the material effect is that the same procedural object cannot be raised again in any subsequent proceedings. It is on this aspect that this paper is based.
International scale
This proscription is projected on an international scale by taking into account the provisions of Article 14.7 of the International Covenant on Civil and Political Rights of New York (ICCPR), ratified by Spain, as well as Article 4 of Protocol 7 of the European Convention on Human Rights (ECHR). Both provisions establish the prohibition of trying or punishing a person for a crime for which he or she has already been convicted or acquitted by a final judgment in accordance with the law and criminal procedure of each country.
It is precisely this international scale that we are going to deal with, i.e. to what extent a foreign judicial decision can have the effect of res judicata in Spain.
Elements of the res judicata exception
In order for this negative or exclusionary effect to be produced, i.e. not to be sanctioned, what elements must be present? This has been answered by the doctrine of the Constitutional Court (STC. 2/1985 of 30 January 1985, 154/1990 of 14 October) and the case law of the Supreme Court (STS. 29 April 1993, 22 June 1994, 17 October 1994 and 882/1997 of 20 June):
Firstly, there must be subjective identity with respect to the subject convicted (or acquitted) abroad and the subject under investigation or accused in the second procedure. This identity is an essential requirement that admits of practically no exception.
Secondly, it is essential to identify the substantial similarity of the facts. They must have a significant internal connection, beyond a mere superficial similarity. This means that the facts must not partially overlap, but must be materially identical (STS 104/2021, 10 February), regardless of the legal qualification made abroad. In the event of doubts about this comparison of facts, the in dubio pro reo principle also applies, so that in the event of doubts, the most favourable interpretation should be applied (ATS 85/2021, Cassation 2401/2020).
Finally, the foreign judgment must be considered final and thus be subject to the effect of res judicata. In Spain, it is clear that final judgments and final acquittals have the force of res judicata, but abroad it is possible that there are files by the prosecution and other types of resolutions that maintain important differences with those Spanish resolutions. Therefore, the relevant question is: What should be the criteria for determining that a foreign decision has the effect of res judicata?
This question has already been resolved by case law, which establishes that what is relevant is not who has issued the decision (whether a Judge or a Prosecutor), but whether the foreign proceedings have been definitively terminated in such a way that they cannot be reopened, always in accordance with foreign legislation (AAN, 24/2021, 16 April). In addition to the above, it is also required that said termination is due to an effective investigation (STS 170/2021, 25 February), with closure for procedural reasons not being sufficient, although a foreign dismissal for lack of evidence can have the effect of res judicata (STJUE of 28 September 2006, Case C-150/05); so that, in short, what is required is that the ius puniendi of that country has been effectively exercised in the foreign proceeding.
In conclusion, if a foreign judgment of conviction or acquittal meets these three requirements , it is possible to enforce it in Spain in order for it to have the effect of res judicata.
