NSW (I'm not 100% sure about other states) has a specific law that allows judges to charge minors who are close to becoming an adult as an adult.The youngest I've heard of is a 14 year old charged as an adult.Note that only the judge has the power to charge a minor as an adult, with some persuasion by the police prosecutor I'm sure. I think other states have something similar.
This legislation was originally meant for violent crimes such as sexual assault, murder and grand arson. As usual it has been used to punish an almost victimless crime - tax evation. Nothing new in this disgusting destroyer of freedom that we call the drug war.