CRC/C/GC/10 page 13 currently in the process of being reviewed. However, the implementation of these guarantees for children does have some specific aspects which will be presented in this section. Before doing so, the Committee wishes to emphasize that a key condition for a proper and effective implementation of these rights or guarantees is the quality of the persons involved in the administration of juvenile justice. The training of professionals, such as police officers, prosecutors, legal and other representatives of the child, judges, probation officers, social workers and others is crucial and should take place in a systematic and ongoing manner. These professionals should be well informed about the child’s, and particularly about the adolescent’s physical, psychological, mental and social development, as well as about the special needs of the most vulnerable children, such as children with disabilities, displaced children, street children, refugee and asylum-seeking children, and children belonging to racial, ethnic, religious, linguistic or other minorities (see paragraphs 6-9 above). Since girls in the juvenile justice system may be easily overlooked because they represent only a small group, special attention must be paid to the particular needs of the girl child, e.g. in relation to prior abuse and special health needs. Professionals and staff should act under all circumstances in a manner consistent with the child’s dignity and worth, which reinforces the child’s respect for the human rights and fundamental freedoms of others, and which promotes the child’s reintegration and his/her assuming a constructive role in society (art. 40 (1)). All the guarantees recognized in article 40 (2), which will be dealt with hereafter, are minimum standards, meaning that States parties can and should try to establish and observe higher standards, e.g. in the areas of legal assistance and the involvement of the child and her/his parents in the judicial process. No retroactive juvenile justice (art. 40 (2) (a)) 41. Article 40 (2) (a) of CRC affirms that the rule that no one shall be held guilty of any criminal offence on account of any act or omission which did not constitute a criminal offence, under national or international law, at the time it was committed is also applicable to children (see also article 15 of ICCPR). It means that no child can be charged with or sentenced under the penal law for acts or omissions which at the time they were committed were not prohibited under national or international law. In the light of the fact that many States parties have recently strengthened and/or expanded their criminal law provisions to prevent and combat terrorism, the Committee recommends that States parties ensure that these changes do not result in retroactive or unintended punishment of children. The Committee also wishes to remind States parties that the rule that no heavier penalty shall be imposed than the one that was applicable at the time when the criminal offence was committed, as expressed in article 15 of ICCPR, is in the light of article 41 of CRC, applicable to children in the States parties to ICCPR. No child shall be punished with a heavier penalty than the one applicable at the time of his/her infringement of the penal law. But if a change of law after the act provides for a lighter penalty, the child should benefit from this change. The presumption of innocence (art. 40 (2) (b) (i)) 42. The presumption of innocence is fundamental to the protection of the human rights of children in conflict with the law. It means that the burden of proof of the charge(s) brought against the child is on the prosecution. The child alleged as or accused of having infringed the penal law has the benefit of doubt and is only guilty as charged if these charges have been proven beyond reasonable doubt. The child has the right to be treated in accordance with this presumption and it is the duty of all public authorities or others involved to refrain from