In my experience, a common mistaken belief is juvenile records magically disappear. There’s even a law out there that reasonably backs up that belief; see §211.271.3. BUT, you must also see §211.321.2(2) which states that if the juvenile’s charge would have been a felony if committed as an adult, then the juvenile records are open to the public as if they were adult criminal records.
The following case, State of Missouri v. Sapien, No. 69575 (Mo. App. W.D., February 22, 2011), illustrates my above point. It involved an adult sodomy trial where the state used the defendant’s juvenile record of rape to convince the judge to order a lengthier prison sentence. The trial court allowed the juvenile record to be admitted in as evidence to enhance sentencing and the appeals court affirmed that use, ruling that §211.321.2(2) essentially trumps §211.271.3.