68. Under Article 86 of the CCP, the prosecutor and the investigator are under an obligation to collect both incriminating and exonerating evidence. Throughout criminal proceedings, the prosecutor must “effect a supervisory control of lawfulness” (Article 43 CCP). F. Provisions on pre-trial detention 1. Power of prosecuting authorities to detain on remand 69. An accused, including a minor, can be detained on remand by decision of an investigator or prosecutor, although minors may be detained on remand only in exceptional circumstances. In cases where the decision to detain has been taken by an investigator without the prior consent of a prosecutor, it must be approved by a prosecutor within twenty-four hours. The prosecutor usually makes this decision on the basis of the file, without hearing the accused (CCP, Articles 152, 172, 201-203 and 377-378). 70. A criminal investigation must be concluded within two months. A prolongation of up to six months may be authorised by a Regional Prosecutor and, in exceptional cases, the Chief Public Prosecutor may prolong the investigations up to nine months. If the period is prolonged, the prosecutor will decide whether to hold the accused in custody (CCP, Article 222). 71. There is no legal obstacle to prevent the prosecutor who has taken the decision to detain an accused on remand, or has approved an investigator’s decision, from acting for the prosecution against the accused in any subsequent criminal proceedings. In practice this frequently occurs. 2. Judicial review of pre-trial detention 72. A person detained on remand has the opportunity immediately to file an appeal with the competent court against the imposition of detention. The court must pronounce its decision within three days of the filing of the appeal (CCP, Article 152 § 5). 73. According to the practice which was current at the time of Mr Assenov’s arrest, the court examines appeals against detention on remand in camera, without the participation of the parties. If the appeal is dismissed, the court does not notify the detained person of the decision taken. 74. The First Criminal Chamber of the Supreme Court has held that, in deciding on such appeals, it is not open to the court to inquire whether there exists sufficient evidence supporting the charges against the detainee, but only to examine the lawfulness of the detention order. A detention order will only be lawful, in cases of persons charged with crimes punishable by less than ten years’ imprisonment, where there is a “real danger” of the accused absconding or reoffending (decision no. 24 in case no. 268/95). 75. In a decision of 17 September 1992, the First Criminal Chamber of the Supreme Court found that the imposition of detention on remand could be contested before a court only once. A new