Q: I am a father of a teen that was assaulted by a drunk adult

A: Significant material facts are missing here. The questions reads like "there I was walking down the street and next thing I know I'm being charged with drunk driving". If I had to guess and read between the lines here, it sounds like this drunk adult was on his property. The teenagers either started as guests and then were asked to leave, or they were trespassing. Either way, without more, the adult's level of intoxication doesn't seem to be a factor yet...Due to the ruckus, Dad shows up and tries to intervene. At some point, I can only guess from the charges, Dad entered the drunk adult's home, and was certainly not an guest at that point (hence trespassing).

I am unsure what the real question is. Only the local prosecutor can charge people with crimes. Police investigate and report their finds to the prosecutor, who ultimately has the charging authority. For whatever reason, the police found Dad to have some criminal liability and not the drunk adult, and the prosecutor agreed. Now, the prosecutor certain could still charge this drunk adult with a crime after further review of the report and if other evidence becomes available. What crime he could be charged with, I don't know; being drunk (and of legal age) on your own property (and not in a car or holding a firearm) isn't in itself a crime. And if people then trespass onto your property while you are drunk, you have a right to defend yourself and your property even when drunk.

Assuming there is a disagreement with how all this is shaping out, it's the prosecutor you need to speak to. Keep in mind that even if they decide to charge the drunk adult, that doesn't mean the other charges on Dad go away. Two opposing people can both be charged with crimes.