Federal courts differ from state courts in that attorneys who are admitted to practice in Federal Court can generally practice in any part of the federal system. It would seem logical, however, to secure counsel in NJ who is familiar with the system there and the players involved. I would suggest that you post a question changing Philadelphia PA to _____, NJ and that you change the Practice Area. Your question is not one involving criminal defense, rather it involves civil litigation and civil rights in particular which is a rather specialized area. I don't have all the choices for Practice Area easily available so I suggest you look carefully through the list to pick on in the civil litigation area for NJ. Good luck.
I agree with Mr. Jones that it is probably better for him to hire a lawyer from New Jersey for a number of reasons. If he is in prison in New Jersey, it will probably be easier for a New Jersey lawyer to meet him face to face. A New Jersey Lawyer will have more familiarity with the Federal Courts trial courts in New Jersey.
Being in New Jersey, it would make sense for him to hire someone who is either in New Jersey or practices there. Attorneys who practices criminal defense often practice civil rights as well, but not always. You'll want to make sure that the attorney your friend hires is experienced in the civil rights field and knows how to litigate a federal case, which is very different from a state court case. I do think searching under New Jersey civil rights for lawyers would be a good place to start and see who's out there. Good luck.