(1) For concurrent criminal offences the court shall impose to a juvenile only one educational measure or only a punishment of juvenile imprisonment, when legal conditions exist for that punishment to be imposed and when the court finds that it should be imposed. (2) The court shall proceed pursuant to provision of paragraph 1 of this Article also in case it establishes that a juvenile had perpetrated a criminal offence prior or after an educational measure or juvenile imprisonment has been imposed. Article 103 Statute of Limitations on Execution of the Juvenile Imprisonment The execution of juvenile imprisonment is barred when the following time periods have elapsed from the date of entering into force of the judgement by which the punishment has been imposed: a) Ten years if the punishment of juvenile imprisonment for a term exceeding five years has been imposed; b) Five years if the punishment of juvenile imprisonment for a term exceeding three years has been imposed; c) Three years if the punishment of juvenile imprisonment for a term not exceeding three years has been imposed. Article 104 Imposing Criminal Sanctions on Adults for Offences They Have Perpetrated as Juveniles (1) An adult who has reached twenty-one years of age may not be tried for a criminal offence he perpetrated as a junior juvenile. (2) If an adult has not reached twenty-one years of age at the time of the trial, he may be tried only for criminal offences for which a punishment of imprisonment for a term exceeding five years has been prescribed. The court may impose on such a person only the appropriate institutional educational measure, taking into account, when considering whether to impose such a measure or not, all the relevant circumstances of the case, in particular the gravity of the criminal offence perpetrated, the time that has elapsed since the perpetration, the conduct of the perpetrator and the purpose of the educational measure. (3) An appropriate institutional educational measure may be imposed on an adult for a criminal offence he perpetrated as a senior juvenile, and under conditions referred to in Article 100 (Juvenile Imprisonment) of this Code, a punishment of juvenile imprisonment may also be imposed. In deciding whether to impose a sanction and which of the sanctions to impose, the court shall take into account all the relevant circumstances of the case, in particular the gravity of the criminal offence perpetrated, the time that has elapsed since its perpetration, the conduct of the perpetrator, as well as the purpose of these sanctions. (4) As an exception to the provision of paragraph 3 of this Article, in lieu of juvenile imprisonment the court may impose a punishment of imprisonment or suspended sentence on an adult who has reached twenty-one years of age at the time of the trial. Regarding rehabilitation, deleting the sentence and legal consequences of the sentence, the sentence of imprisonment in this case shall have the same legal effect as a sentence to juvenile imprisonment. Article 105 Imposing Educational Measures on Young Adults (1) The court may impose an appropriate institutional measure on a perpetrator who has perpetrated a criminal offence as an adult, but who has not reached twenty-one years of age at the time of trial, if, given his personality and circumstances in which he perpetrated the criminal offence, it may reasonably be expected that the educational measure would have the same result as an imprisonment sentence. (2) Under the conditions prescribed by this Code, the court may impose on a young adult on whom it had imposed an educational measure any security measure prescribed in this Code, other than the security 31