Are you asking, if a minor is taken to an E.R. after an accident or overdose, can they do a tox screen as part of their emergency care? Yes.
If a person has illegal drugs on their person at the E.R., the illegal drugs may be turned over to the police. As it's illegal to possess illegal drugs, the person may be prosecuted for possessing them.
If the person possessed illegal drugs, and tested positive for the same drugs, the odds are that they tested positive because they were using their illegal drugs.

