Yes, the police can question a minor without their parent(s) present if that minor is not in custody. This often happens when an officer has a reasonable belief that a minor has violated the law. They can detain the minor to conduct an investigation. During such a detention, the police are not required to let a minor call their parents. Nowhere in the constitution does it say that parents must be present during an interrogation of their child; accordingly there is no constitutional right to have a parent present during such questioning. However, if your child made certain incriminating statements regarding the incident, what could be relevant is if your child asked for a parent to be present and the request was ignored. If statements were not voluntarily and freely made, than these statements may possibly be excluded as evidence in any case that may be brought against your child. If you child was under arrest, there are also Miranda (i.e. the reading of your rights) implications. Since you gave no details its hard to say more. If you think that Yuri child's rights may have been violated then you should consult directly with a criminal law attorney in your area. Specific rules regarding the questioning of a child vary from state-to-state.