If you want to know how prosecutors like Mueller and Rosenstein and their Pit Bull, Weissmann, became judge and jury, look no further than Plea Bargaining. It has totally corrupted the US Justice System.
https://www.cairn.info/revue-internationale-de-droit-penal-2012-1-page-109.htm#
Plea Bargaining in the United States: a Perversion Of Justice
Criminal justice today is for the most part a system of pleas, not a system of trials.”
Justice Anthony Kennedy, Missouri v. Frye (2012)
Our entire criminal justice system has shifted far away from trials and juries and adjudication to a massive system of sentence bargaining that is heavily rigged against the accused citizen.
William Young, (then) Chief Judge, U.S. District Court, Massachusetts, U.S. v. Richard Green (2004)
Read full article at above link.