Possession of child pornography can be charged at the State level, and often is. It can also be charged as a Federal crime. So when I said this was Federal, I was specifically referring to the simulated child pornography in the comics. There may be a State law counterpart, but probably not. I mentioned that it only became illegal in 2003, because if Tera is now 18, in 2003 she would have been 11 or 12... if the images were drawn before then, it probably would not have been illegal. Even if they were drawn post 2003, it may not be charged. If you wanted to avoid going down this path, you could easily have the prosecutor bring Tera in to discuss the possible molestation, and not have him charged Federally- just because of the gray area of the law and also the elapsed time many prosecutors wouldn't want to mess with it.
If the feds need to step in, usually what happens that they are notified by the local authorities and both cases are charged simultaneously (charged in Federal court while also charged in local county court). The prosecutor would be a U.S. Attorney, but the defense attorney could be the same person, and usually is. There is a U.S. District Court in Seattle, and that is where the FBI and U.S. Attorney would be located. The defense attorney would remain the same. The process is somewhat different in that it is very difficult to beat Federal charges, they take a longer time to build a case and they pretty much always have the defendant dead-to-rights before the case is filed. Tera and her dad would be notified through their attorney.
As far as notification... the U.S. Attorney would probably contact the defense attorney, or just send mail an indictment to the father in prison and the attorney. Most of the time, the local prosecutor will tell the defense attorney, that the charge is being sent up to the feds, and he will know what is coming. Then the defense attorney would enter his appearance in the Federal case too.