6.  The applicant was born in 1974 and lives in Cologne. At the time of the events at issue he had been a police officer. He was subsequently dismissed when his conviction for inflicting bodily harm causing death while exercising a public office (Körperverletzung im Amt mit Todesfolge) as a consequence of the trial which forms the subject of the present application became final. 7.  Prior to the proceedings at issue the applicant had already been the subject of preliminary investigations by the public prosecution authorities on eight separate occasions on suspicion of having caused bodily harm while on duty. At the time of the events at issue, seven of these preliminary proceedings had been discontinued in lack of sufficient evidence for the charges and one of the proceedings was still pending. In 2001 he had further been convicted of two counts of libel (Beleidigung) and compulsion (Nötigung) committed in the course of police operations. 8.  On 11 May 2002 the applicant was called to assist other police officers in arresting a man who was acting violently. The man (“the victim”) was overpowered using force by the police officers, including the applicant, arrested and transferred to the Cologne Eigelstein Police Station. One police officer sustained minor injuries during the victim’s arrest. The arrested person was subsequently transferred to a hospital where he fell into a coma and died without having regained consciousness. 9.  Police officer G. and his female colleague H. belonged to an earlier shift but were still present at the police station when the victim was brought to the station. At the time of the events at issue G. and H. had an intimate relationship while G. was married to another woman. They witnessed the victim’s ill-treatment by several police officers at the police station without helping the victim and later discussed the events and what, if any, further action was required in view of the incident. 10.  On 12 May 2002 H. informed her former supervisor that G. and herself had witnessed several police officers surrounding the victim and repeatedly and jointly kicking him in the head, body, arms and legs as he had lain handcuffed on the floor of the “watergate”, a tapered room whose width decreased from approximately 2.5 meters to 1.5 meters and which functioned as the police station’s entry room. The victim had also been kicked and beaten later in a cell. 11.  H.’s former supervisor immediately informed his hierarchical superiors who summoned G. and H. to the police station and questioned them later that day. G. and H. named several police officers, including the applicant, as participants in the victim’s ill-treatment and identified several of them, including the applicant, during an identity parade. 12.  All officers named by G. and H. were suspended from active duty. Criminal investigations were instituted against those officers as well as against G. and H. and conducted by a special team (Sonderkommission) established for this purpose. The head of the Cologne Eigelstein Police Station, who had not been involved in the events at issue, was posted to another police station with a view to enabling an impartial clarification of the circumstances of the case. 13.  On 23 May 2002 counsel for the witnesses G. and H. submitted their written testimonies on the incident of 11 May 2002. As recommended by their respective counsel, G. and H. did not specify their own actions. 14.  The criminal investigations against G. and H. on suspicion of having participated in the victim’s ill-treatment, of not having rendered assistance to the victim and of having attempted to obstruct the prosecution of the police officers involved in the ill-treatment, were discontinued on 24 February 2003. The prosecution authorities specified that there was no evidence that G. and H. had actively participated in the ill-treatment. They further found that in view of the fact that the events had occurred within a short space of time it had been impossible for G. and H. to intervene and effectively prevent the ill-treatment. Furthermore, a psychiatric opinion obtained by G. and H.’s respective counsel from a professor at Munich university hospital expressed doubts as to whether G. and H. would have been personally capable of confronting their colleagues and helping the victim while having regard to the psychological pressure they had been exposed to at the time of the events at issue. 15.  On the same date, 24 February 2003, the applicant and five other police officers involved in the events were charged with jointly inflicting bodily harm causing death while exercising a public office (gemeinschaftliche Körperverletzung im Amt mit Todesfolge) before the Cologne Regional Court sitting in a jury formation (Schwurgericht) with three professional and two lay judges (Schöffen).
The subsequent trial was conducted in the period from 26 June to 25 July 2003. 16.  On 8 July 2003, the fifth of in total eleven hearing days, witnesses G. and H., the only eye witnesses of the events in the “watergate” and the cell, testified in court. In reply to the Regional Court’s related question they denied having an intimate relationship. 17.  G. gave an account of his recollection of previous statements made by him in the course of the preliminary proceedings and answered questions posed by the presiding judge, another judge and the public prosecutor. Then counsel assisting the witness declared that the latter would not answer questions by the accused, defence counsel or by the victim’s relatives acting as joint plaintiffs to the prosecution (Nebenkläger). Counsel pointed out that the criminal investigations against the witness for participating in the victim’s ill-treatment had been discontinued but could be reopened and there was thus a risk that the witness could incriminate himself. The Regional Court observed that two of the accused, including the applicant, had indeed declared in the course of the trial that G. had participated in the ill-treatment. He was therefore entitled not to reply to questions of the defence after having testified and having answered questions by members of the court and the prosecutor. Consequently, the court ordered that the witness be granted the right not to answer questions posed by defence counsel or the accused pursuant to section 55 of the Code of Criminal Procedure (see “Relevant domestic law” below). The court further ordered that G. not be put under oath. 18.  Subsequently, witness H. testified, gave an account of her previous testimonies during the investigations, and answered questions by the court and an expert witness. She refused to answer questions by the defence counsel and counsel for the victim’s relatives. Counsel for one of the applicant’s co-accused formulated questions to be put to H. by the court. Counsel for H. then declared that H. would also not answer further questions by the court since there was a risk that the witness could incriminate herself. The Regional Court observed that criminal investigations had been pending against H. on suspicion of not having rendered assistance to the victim and of having attempted to obstruct the prosecution of the police officers involved in the ill-treatment. The court thus ordered that H. be granted the right not to testify pursuant to section 55 of the Code of Criminal Procedure (see “Relevant domestic law” below) and for this reason also refrained from submitting the questions formulated by counsel to the witness. The Court specified that once a witness had invoked his or her right to remain silent pursuant to the said provision any further questions were inadmissible. Furthermore, H. had explicitly stated that she would not answer any further questions even if put by the court. 19.  On 13 July 2003 the applicant and another accused applied for two witnesses to be examined by the court with a view to demonstrating that G. and H. had lied to the court as regards their extramarital affair. They further alleged that G. had not told the truth concerning certain information provided on his past career as a police officer and regarding an intimate relationship with a further female colleague. The Regional Court, assuming that these allegations were correct, considered that the hearing of the proposed witnesses could be dispensed with. 20.  On 14 July 2003 the applicant requested that G. and H.’s statements be excluded as evidence from the trial. 21.  In its judgment of 25 July 2003 the Regional Court held that the accused police officers by jointly and wilfully inflicting bodily harm on the victim had negligently caused the latter’s death and found them guilty as charged. It sentenced the applicant to a suspended prison term of one year and four months.
(a)  The facts established by the Cologne Regional Court 22.  According to the facts as established by the Regional Court, the victim suffered from an acute boat of psychosis. He threatened two police officers with death who had arrived at the victim’s flat following a neighbour’s emergency call. The officers requested reinforcements, used pepper spray and subsequently subdued the victim using considerable force. The victim thereupon entered into a state of “excited delirium” and displayed extreme agitation, violent behavior, insensitivity to pain, and “superhuman” strength. The applicant and another police officer then arrived as further reinforcements, repeatedly hit the victim’s legs and managed to shackle the victim who nonetheless continued to struggle. No police officer involved in the arrest was aware that the victim was suffering from a psychotic bout. One of the police officers involved, police officer A., sustained minor injuries. 23.  The police officers transported the handcuffed and shackled victim to the Cologne Eigelstein Police Station. In the “watergate” the victim fell to the ground. The officers stood in a circle around the victim and jointly kicked and beat him while being aware that he did no longer present a serious danger. They were angry that the victim continued with his futile resistance which was perceived as particularly unruly. They also wanted to take revenge for their colleague A.’s injuries. As a consequence of his ill‑treatment the applicant’s nose started bleeding. One of the officers called an ambulance, a procedure generally observed in the event a person in police custody sustains, even minor, injuries. 24.  The victim was then pulled from the “watergate” to a cell, leaving a clearly visible trail of blood on the floor. Some officers, including the applicant, continued to jointly beat and kick the victim who was no longer offering any resistance in the cell, leaving stains of the victim’s blood on the wall. 25.  The victim was then transferred to a hospital where the medical personnel at first did not recognise the psychotic bout and did not order that handcuffs and shackles be removed. The victim’s pulse and breathing were not checked continuously. Following the victim’s apnoea and cardiac arrest, he was transferred to the intensive care unit where he was reanimated, possibly causing rib fractures. The victim sustained irreparable brain damage and died on 24 May 2002. 26.  The coroner concluded on the basis of a post-mortem that the victim had collapsed because of psychic excitement that had resulted in an “excited delirium”. The coroner could not decide whether the force used by the police officers or the medical maltreatment in the hospital had caused the victim’s death.
(b)  The assessment of the testimonies of witnesses G. and H. 27.  The Regional Court declared that it had based its finding on the victim’s ill-treatment in the “watergate” and in the cell on the statements of the witnesses G. and H. While the fact that the defendant had been deprived of the opportunity to examine the witnesses required the court to subject the credibility of their testimonies to particular scrutiny, it had nevertheless not been necessary to exclude them altogether. 28.  In this context the Regional Court noted that there was no plausible reason why the witnesses should have wrongly accused their colleagues. They did not have any tangible benefits from their testimonies but, as also pointed out by the psychiatric expert who had examined the witnesses, risked on the contrary being branded as traitors by other police officers. They had further risked incriminating themselves for not having assisted the victim. 29.  The court was further of the opinion that allegations indicating that G. had accused his colleagues with a view to concealing a possible own involvement in the victim’s ill-treatment were not convincing. Even assuming such involvement, there had been no reasons for G. to expect that any of the police officers participating in the ill-treatment would disclose the underlying events at their own initiative. In fact such allegations were made for the first time by one of the accused after G. and H. had revealed the circumstances of the case. 30.  The court further observed that the witnesses – from their point of view – had a plausible justification for their decision not to answer questions by the defence. G. and H. had an intimate relationship while G. was married to another woman. As it had had transpired already in the course of the preliminary proceedings, they had to expect questions concerning their intimate relationship in a highly publicised trial by the defence with a view to casting doubt on their credibility. 31.  The court considered that the witnesses’ testimonies were credible, consistent and that there was nothing to establish that they had coordinated their testimonies. The psychiatric expert who had examined the witnesses had also confirmed that their description of the events at issue was credible and their behaviour plausible while taking into account the strain G. and H. were exposed to. In contrast, the account of the events given by the applicant and the co-accused and their denial of any involvement in the applicant’s ill-treatment in the “watergate” were contradictory and not supported by the further available evidence. 32.  The witnesses’ descriptions of the events on their part were corroborated at least in part by the statements of some of the accused or other evidence. For instance, the applicant himself had conceded that in the cell he had kicked the victim once in the hip as a warning and with a view to preventing a possible attack by the latter. Another accused, D., had confessed that he had also beaten the victim one time in the cell, not because it was necessary to prevent an attack but rather because he could not control his anger at the victim. Police officer A. who had sustained minor injuries on the occasion of the victim’s arrest and had been heard as a witness on the occasion of the trial had testified that when the victim had been taken to the ambulance one of the accused police officers had told him “We have taken revenge for you”. In the court’s view these additional testimonies constituted evidence that the police officers’ treatment of the victim had not constituted an ordinary and appropriate reaction to the resistance of an arrested person. The Regional Court further referred to two medical expert opinions confirming that while the injuries sustained by the victim were not particularly serious and had not directly led to his death, they could nevertheless be aligned with the description given by G. and H. of his ill-treatment in police custody. 33.  Having regard to the above considerations, the Regional Court concluded that there was nothing to cast doubt on the veracity of G. and H.’s testimonies to the extent they concerned the circumstances of the victim’s ill-treatment. The court conceded that it could not be established whether the force used by the police officers or, alternatively, the medical maltreatment in the hospital had caused the victim’s death and considered that this uncertainty had a mitigating effect on the sentences imposed. The Regional Court nevertheless maintained that the ill-treatment in the “watergate” had led to the victim’s bleeding and consecutive transport to the hospital and that there had therefore been a causal connection between the physical abuse in police custody and the latter’s death. Since the co-accused had acted jointly their respective participation in the ill-treatment was imputable to each of them. 34.  On 28 July 2003 the applicant lodged an appeal on points of law. In his appeal brief of 1 December 2003 he complained in particular that the testimonies of witnesses G. and H. had not been excluded despite the defence’s inability to examine those witnesses in breach of Article 6 § 3 (d) of the Convention. 35.  On 2 July 2004 the Federal Court of Justice dismissed the applicant’s appeal on points of law. 36.  On 16 August 2004 the applicant lodged a constitutional complaint. He argued that the Regional Court’s reliance on the testimonies of witnesses G. and H. had violated his right to a fair trial pursuant to Article 6 §§ 1 and 3 (b) and (d) of the Convention because the Regional Court had failed to provide for a possibility for the defence to examine witnesses G. and H. 37.  On 27 December 2006 the Federal Constitutional Court refused to admit the applicant’s constitutional complaint for examination (no. 2 BvR 1657/04). The decision was served on the applicant on 11 January 2007. 38.  The Federal Constitutional Court observed that the constitutional right to a fair trial was both affirmed and substantiated by Article 6 §§ 1 and 3 of the Convention; that it needed to be concretised on a case-by-case basis; that specific procedural requirements could only be deduced from it if basic requirements of the rule of law were at stake; that the accused had to have access to and a right of participation in the establishment of the facts and that illegally obtained evidence had not always to be excluded. It emphasised that the domestic courts were under a constitutional obligation to take Article 6 §§ 1 and 3 of Convention, as interpreted by this Court, into account and to duly consider the factors found to be relevant by this Court in balancing competing rights when deciding the case before them. 39.  Turning to the circumstances of the case at hand, the Federal Constitutional Court held that there had been no violation of the applicant’s constitutional right to a fair trial and Article 6 § 3 (d) of the Convention. Although the criminal courts had based their findings on the testimonies of witnesses G. and H. whom the defence had had no opportunity to question at any stage of the proceedings, the right to a fair trial did not require that these testimonies be excluded. 40.  The witnesses’ autonomous decision not to answer questions had been based on a sustainable ground, namely their right to remain silent. Public authorities had not caused the applicant’s inability to examine or have examined witnesses G. and H. to such an extent as to warrant the exclusion of their testimonies. The applicant had not had a right to be present during the police interrogation of G. and H. who at that time had been co-suspects. There had been no need to allow for the presence of the applicant’s counsel during the pre-trial examinations of G. and H. because it had not been foreseeable that the witnesses would refuse to answer questions of the defence in court. The witnesses had freely chosen not to answer questions of the defence. H. had declared that she would not answer further questions by the court. The state authorities had thus not been responsible for the inability of the defence to confront the witnesses. Furthermore, the Regional Court had been aware of the reduced evidentiary value of the witnesses’ testimonies. It had extensively questioned the witnesses in open court and, taking into account expert advice, had carefully assessed the testimonies as regards their content, development and possible adjustments. It had thus analysed the testimonies extensively, critically and thoroughly. 41.  Following expiry of the probation period (Bewährungszeit), the Regional Court by a decision of 17 July 2006 remitted the applicant’s sentence.