Related Rule
Practice Relating to Rule 100. Fair Trial Guarantees
Section M. Right to appeal
In 2010, in the Couso case, the Criminal Chamber of Spain’s Supreme Court was called upon to decide an appeal in the case concerning the killing of a Spanish journalist in Baghdad on 8 April 2003 by troops of the United States of America. With regard to the Prosecution Service’s preliminary question on the inadmissibility of the appeal in question, the court held:
4. … An interpretation contrary to the feasibility of an appeal process … and a pronouncement on the substantive issues [of the case] would contradict … the fundamental right of the appellants to a due process, including the prohibition on a lack of a proper defence and the right to appeal.
It should be noted, in addition, that as judgement 4945/1990 of this Chamber of 20 January 1992 recalls, “Article 5(4) of the Law on Judicial Power [1985] establishes that the infringement of a constitutional precept is sufficient grounds for seeking an appeal if the process is to continue”. In addition, Article 5(7) of the same Law provides that “the rights and freedoms recognized in chapter 11 of title 1 of the Spanish Constitution are integrally binding on all judges and tribunals, and are guaranteed under their effective judicial protection”. It can be deduced from both provisions that any final order, the effects of which are equivalent to a sentence, must provide access to an appeal when [the order] has prevented access to the jurisdiction of the court in violation of constitutional rights. …
In addition, concerning the order to terminate the proceedings [currently under review] … the violation of the right to due process can take place not only when there is a person accused of the acts [of the case] but also when the prosecution has been circumvented by the court, thus denying the plaintiffs the possibility of defending their legitimate interests in a trial with all the [judicial] guarantees.
This broadening of the cases in which an appeal is possible, with regard to definite orders to terminate [proceedings] that affect fundamental rights, is a consequence of the “direct third-party effect of the fundamental rights” and of the general mandate of effective protection of these established in the cited Article 5(7)(1) of the Law on Judicial Power.
In the same sense, recent jurisprudence such as that emerging from STS 1172/20009 [Supreme Court judgement] of 22 October 2009 admits that the termination [of the proceedings] must be subject to an appeal, as its decision is equivalent to an acquittal …
As a result, the dismissal [of the proceedings] has denied the plaintiffs their right to a trial in which they could have defended their legally recognized interests, with a substantiation of facts that these could not contest, and despite the existence of prima facie evidence that the offences attributed to the defendants were carried out.
It is therefore appropriate to dismiss the … [preliminary question] of the Prosecution Service. 
Spain, Supreme Court, Couso case, Judgment, 13 July 2010, Section II(I), Primero, § 4, p. 6; see also Section II(II), Tercero, §§ 1–2, p. 9.
[emphasis in original]
The Court upheld the appeal against the order of 23 October 2009 by the Third Section of the Criminal Chamber of the Spanish National Court, which declared the termination of the proceedings, and held that “the proceedings must continue, and the outstanding preparatory enquiries must be undertaken, as well as any others arising from the clarification of the events under investigation.” 
Spain, Supreme Court, Couso case, Judgment, 13 July 2010, Section III, pp. 20–21.