E/CN.4/2000/4/Add.2 page 9 presumption of innocence (art. 6) and from the possibility of appeal and cassation (art. 67) (on the implementation of these provisions, see paras. 69-70 below). 33. Preventive detention, if considered necessary for the purposes of the police investigation, is regulated as follows (arts. 24-37). Upon expiration of the 24-hour period after arrest, the police investigators must provide the person concerned with a detention order, which remains in effect for 20 days. The order can be extended, if necessary, for a period of 40 days, with the authorization and under the supervision of the prosecutor, or at his own initiative after examining the file. After this first 60-day period - during which the detained person need not be presented before the prosecutor another extension can be ordered, if considered necessary, for a period not exceeding 20 days. This second extension must be authorized by a judge. After transmittal of the file to the tribunal of first instance, the judge in charge of the case can grant another extension for 30 days. This may be followed, upon decision of the president of the tribunal, by a supplementary 60 days if considered necessary for the completion of file work and investigation of the case. 34. In the event of appeal, the court can order another extension of the detention order for a period of 30 days, followed, if necessary, by another period of 60 days upon decision of the President of the Court of Appeal. If the case goes to the Supreme Court on cassation, the detention can yet again be extended for 50 days by a collegiate body of that Court (the “Petty Bench”) and for another 60 days by decision of the President of the Supreme Court. If the accused has not been brought to trial after these 110 days, he must be released. The maximum length of detention before trial and judgement is therefore 400 days. 35. Throughout the investigation, the accused may call witnesses. At every stage, a decision prolonging detention must be notified to the accused. At any time during the procedure and especially on the occasion of a request for prolongation of detention, if the investigation is completed, the accused can: Either be sent to appear before the court; in this case, the case file is forwarded to the prosecutor; Or be purely and simply released if the offence has not been proved, if the charges are insufficient or if the detention was declared illegal following a habeas corpus request (“pre-trial hearing”); Or be released conditionally or on bail (possibly on bail posted by a relative), so that he may appeal before the court at liberty. During the first 20 days of detention, the amount of bail is determined by the police and can be challenged before a judge. 3. The habeas corpus procedure 36. The so-called “pre-trial hearing” - a procedure which displays all the characteristics of habeas corpus - is regulated in detail by articles 77 to 83 of the Code of Criminal Procedure. It is conducted as follows.