Police officers are allowed to question people as part of investigations of criminal offenses.  There are limits to that ability.  If a person is a suspect in a case, an officer should tell them of their "Miranda rights." that they have the right to remain silent and the right to have an attorney present before questioning.  If the officer fails to advise them of these rights, and if a judge later decides the statements were taken improperly, the judge can refuse to allow the statements to be used in court.  

Where the suspect is under age 18, the officers should be careful to advise the child of his or her rights, including the right to have a parent present during questioning.  The officer should be careful not to intimidate the child during questioning.  A judge can decide later that the child was questioned improperly, and that can result in the statements being thrown out.   If the judge decides the questioning was proper, the statements can still be used even if the child wasn't advised of their rights.  Each case is different, and not all judges rule the same way on the issue of whether a specific statement was taken illegally.  It would be a good idea, if you have been questioned, to discuss this issue fully with an attorney who is familiar with all the facts of the case.