9 preside over courts or tribunals (composed of a single judge or of several members), including professional and lay magistrates as well as administrative boards (for example the Scottish and Scandinavian systems) or other more informal community and conflict resolution agencies of an adjudicatory nature. The procedure for dealing with juvenile offenders shall in any case follow the minimum standards that are applied almost universally for any criminal defendant under the procedure known as "due process of law". In accordance with due process, a "fair and just trial" includes such basic safeguards as the presumption of innocence, the presentation and examination of witnesses, the common legal defences, the right to remain silent, the right to have the last word in a hearing, the right to appeal, etc. (See also rule 7.1.) 15. Legal counsel, parents and guardians 15.1 Throughout the proceedings the juvenile shall have the right to be represented by a legal adviser or to apply for free legal aid where there is provision for such aid in the country. 15.2 The parents or the guardian shall be entitled to participate in the proceedings and may be required by the competent authority to attend them in the interest of the juvenile. They may, however, be denied participation by the competent authority if there are reasons to assume that such exclusion is necessary in the interest of the juvenile. Commentary Rule 15.1 uses terminology similar to that found in rule 93 of the Standard Minimum Rules for the Treatment of Prisoners. Whereas legal counsel and free legal aid are needed to assure the juvenile legal assistance, the right of the parents or guardian to participate as stated in rule 15.2 should be viewed as general psychological and emotional assistance to the juvenile-a function extending throughout the procedure. The competent authority's search for an adequate disposition of the case may profit, in particular, from the co-operation of the legal representatives of the juvenile (or, for that matter, some other personal assistant who the juvenile can and does really trust). Such concern can be thwarted if the presence of parents or guardians at the hearings plays a negative role, for instance, if they display a hostile attitude towards the juvenile, hence, the possibility of their exclusion must be provided for. 16. Social inquiry reports 16.1 In all cases except those involving minor offences, before the competent authority renders a final disposition prior to sentencing, the background and circumstances in which the juvenile is living or the conditions under which the offence has been committed shall be properly investigated so as to facilitate judicious adjudication of the case by the competent authority. Commentary Social inquiry reports (social reports or pre-sentence reports) are an indispensable aid in most legal proceedings involving juveniles. The competent authority should be informed of relevant facts about the juvenile, such as social and family background, school career, educational experiences, etc. For this purpose, some jurisdictions use special social services or personnel attached to the court or board. Other personnel, including probation officers, may serve the same function. The rule therefore requires that adequate social services should be available to deliver social inquiry reports of a qualified nature. 17. Guiding principles in adjudication and disposition 17.1 The disposition of the competent authority shall be guided by the following principles: