CRC/C/GC/24 The upper age limit of juvenile justice (or age of criminal majority) 37. The upper age limit to the juvenile justice system/ the age of criminal majority is the limit of age after which a person who commits a crime is considered an adult and answers of this offence before the adult criminal courts. The upper age limit of the juvenile justice system/ criminal majority is universally fixed at 18 years of age and corresponds to the definition of a child contained in article 1 of the Convention. This means that every person under the age of 18 years at the time of the alleged commission of an offence has the right to be treated in accordance with the rules of juvenile justice, in a specific and specialized system, different from the criminal one applicable to adults. The application of juvenile justice system 38. The juvenile justice system should apply to children who are above the minimum age of criminal responsibility but below the age of 18 years at the time of the commission of the offence. 39. In relation with the upper age limit of the juvenile justice system, the Committee wishes to remind States parties that they have recognized the right of every child in conflict with the law to be treated in accordance with the provisions of art. 40 of the Convention. These special rules – both in terms of special procedural rules and of rules for diversion and special measures – should apply, starting at the minimum age of criminal responsibility set in the States party, for all children who, at the time of their alleged commission of an offence, have not yet reached the age of 18 years. 40. The Committee, therefore, recommends that those States parties which limit the applicability of their juvenile justice rules to children under the age of 16 years (or lower), or which allow by way of exception that certain children are treated as adult offenders (for example, because of the category of the offence), should change their laws with a view to achieving a non-discriminatory full application of their juvenile justice rules to all persons under the age of 18 years at the time of the offence (see also general comment No. 20 (2016) on the implementation of the rights of the child during adolescence, paragraph 88). 41. Juvenile justice systems should also extend protection to child offenders who were below the age of 18 at the time of the commission of the offence but who turn 18 during the trial or during the period of sentence. 42. The Committee notes with appreciation that some States parties allow for the application of the rules and regulations of juvenile justice to persons aged 18 and older, usually until the age of 21, whether as a general rule or by way of exception. Systems with two minimum ages of criminal responsibility 43. Several States parties use two minimum ages of criminal responsibility: children in conflict with the law who at the time of the commission of the crime are at or above the lower minimum age but below the higher minimum age are assumed to be criminally responsible only if they have the required maturity in that regard. The assessment of this maturity is often left to the court/judge, sometimes without the requirement of involving a psychological expert (who are often not available in developing states), and results in practice in the use of the lower minimum age in cases of serious crimes. The system of two minimum ages is often not only confusing, but leaves much to the discretion of the court/judge and may result in discriminatory practices. Birth certificates and age determination 44. A child who does not have a birth certificate must be provided with one promptly and free of charge, whenever it is required to prove age. If there is no proof of age by birth certificate, the authority, with the assistance of social workers, if available, should accept all documentation such as notification of birth, extracts from birth registries, baptismal or equivalent documents, or school reports. Documents that are available should be considered genuine unless there is proof to the contrary. Authorities should allow for interviews with parents or testimony by parents regarding age, or for permitting questionnaires to be filed by teachers or religious or community leaders who know the age of the child. 10