In either case, it doesn't matter. The point is the prosecutor really seems to be taking race into account on juvenile cases. Were they favoring black kids or unduly penalizing them is immaterial.
So when someone raises the specter of racism in a powerful public office like this, the accusation warrants investigation if nothing else. And other people here have asked for hundreds of samples, but this prosecutor's data set (which is really the thing in question here) is really not that large.
What's more, it loses sight of the real problem! The real problem is a curious girl is being overly punished for experimenting. The laws that put her in this jeopardy should also be under attack in addition to investigating the racist factors that come to light.