Indien voor de verdediging geen behoorlijke en effectieve mogelijkheid heeft bestaan om een getuige te (doen) ondervragen, kan het gebruik van een door die getuige afgelegde verklaring in strijd komen met art. 6 EVRM. De uitspraak van het EHRM in de zaak Schatschaschwili tegen Duitsland (EHRM 15 december 2015, nr. 9154/10) houdt daaromtrent onder meer het volgende in:
"101. The Court's primary concern under Article 6 § 1 is to evaluate the overall fairness of the criminal proceedings (see, inter alia, Taxquet v. Belgium [GC], no. 926/05, § 84, ECHR 2010, with further references). In making this assessment the Court will look at the proceedings as a whole, including the way in which the evidence was obtained, having regard to the rights of the defence but also to the interest of the public and the victims in seeing crime properly prosecuted (see Gäfgen v. Germany [GC], no. 22978/05, §§ 163 and 175, ECHR 2010) and, where necessary, to the rights of witnesses (see Al-Khawaja and Tahery, cited above,
§ 118, with further references, and Hümmer, cited above, § 37).
(...)
105. (...) the use as evidence of statements obtained at the stage of a police inquiry and judicial investigation is not in itself inconsistent with Article 6 §§ 1 and
3 (d), provided that the rights of the defence have been respected. As a rule, these rights require that the defendant be given an adequate and proper opportunity to challenge and question a witness against him - either when that witness is making his statements or at a later stage of the proceedings (see Al-Khawaja and Tahery, cited above, § 118, with furtdher references; (...)).
(...)
107. According to the principles developed in the
Al-Khawaja and Tahery judgment, it is necessary to examine in three steps the compatibility with Article 6 §§ 1 and 3 (d) of the Convention of proceedings in which statements made by a witness who had not been present and questioned at the trial were used as evidence (ibid., § 152). The Court must examine
(i) whether there was a good reason for the non-attendance of the witness and, consequently, for the admission of the absent witness's untested statements as evidence (ibid., §§ 119-25);
(ii) whether the evidence of the absent witness was the sole or decisive basis for the defendant's conviction (ibid., §§ 119 and 126-47); and
(iii) whether there were sufficient counterbalancing factors, including strong procedural safeguards, to compensate for the handicaps caused to the defence as a result of the admission of the untested evidence and to ensure that the trial, judged as a whole, was fair (ibid., § 147).
(...)
110. The Court considers that the application of the principles developed in Al-Khawaja and Tahery in its subsequent case-law discloses a need to clarify the relationship between the above-mentioned three steps of the Al-Khawaja test when it comes to the examination of the compliance with the Convention of a trial in which untested incriminating witness evidence was admitted. (...)
113. The Court notes that in a number of cases following the delivery of the Al-Khawaja judgment it took an overall approach to the examination of the fairness of the trial, having regard to all three steps of the Al-Khawaja test (...). However, in other cases, the lack of a good reason for a prosecution witness's absence alone was considered sufficient to find a breach of Article 6 §§ 1 and 3 (d) (...). In yet other cases a differentiated approach was taken: the lack of good reason for a prosecution witness's absence was considered conclusive of the unfairness of the trial unless the witness testimony was manifestly irrelevant for the outcome of the case (...). The Grand Chamber, in the light of the foregoing (see paragraphs 111-112), considers that the absence of good reason for the non-attendance of a witness cannot of itself be conclusive of the unfairness of a trial. This being said, the lack of a good reason for a prosecution witness's absence is a very important factor to be weighed in the balance when assessing the overall fairness of a trial, and one which may tip the balance in favour of finding a breach of Article 6 §§ 1 and 3 (d).
(...)
117. The Court observes that in Al-Khawaja and Tahery, the requirement that there be a good reason for the non-attendance of the witness (first step), and for the consequent admission of the evidence of the absent witness, was considered as a preliminary question which had to be examined before any consideration was given as to whether that evidence was sole or decisive (second step; ibid., § 120). "Preliminary", in that context, may be understood in a temporal sense: the trial court must first decide whether there is good reason for the absence of the witness and whether, as a consequence, the evidence of the absent witness may be admitted. Only once that witness evidence is admitted can the trial court assess, at the close of the trial and having regard to all the evidence adduced, the significance of the evidence of the absent witness and, in particular, whether the evidence of the absent witness is the sole or decisive basis for convicting the defendant. It will then depend on the weight of the evidence given by the absent witness how much weight the counterbalancing factors (third step) will have to carry in order to ensure the overall fairness of the trial.
118. Against that background, it will, as a rule, be pertinent to examine the three steps of the Al-Khawaja-test in the order defined in that judgment (see paragraph 107 above). However, all three steps of the test are interrelated and, taken together, serve to establish whether the criminal proceedings at issue have, as a whole, been fair. It may therefore be appropriate, in a given case, to examine the steps in a different order, in particular if one of the steps proves to be particularly conclusive as to either the fairness or the unfairness of the proceedings (see in this connection, for instance, Nechto v. Russia, no. 24893/05, §§ 119-25 and 126-27, 24 January 2012; Mitkus v. Latvia, no. 7259/03, §§ 101-102 and 106, 2 October 2012; Gani, cited above, §§ 43-45; and Şandru, cited above, §§ 62-66, in all of which the second step, that is, the question whether the evidence of the absent witness was sole or decisive, was examined before the first step, that is, the question whether there was a good reason for the witness's absence)."