I can’t remember any special counsel not prosecuting someone. Fitz knew right away no crime was committed, but like Inspector Javier he kept “investigating” until he nailed Scooter Libby in a perjury trap. Hopefully, Mueller has higher ethics than that, but the standard is pretty low in the Washington swamp.
http://www.cbsnews.com/news/john-danforth-special-counsel-speaks-about-mueller-probe/
...Former Republican Sen. John Danforth was the last special counsel to investigate possible wrongdoing by the executive branch. In 2000, he cleared the Clinton administration in the 1993 siege of the Branch Davidian compound near Waco, Texas...