Appointments of "special counsels" in the United States government are historically very rare and only called upon to investigate politically complicated matters, but they have been in the news lately as Deputy Attorney General Rod Rosenstein appointed a special counsel to investigate possible Russian interference in the 2016 Presidential Election. The news of a special counsel is causing both Americans and people around the world to ask "What is a special counsel and what does s/he do?"
The U.S. Constitution grants federal law enforcement powers to the Executive branch, under the control of the U.S. President and the Department of Justice (DOJ). Congress has little role beyond its to conduct oversight hearings and compel witnesses to testify before Congress in some instances. However, in the rare event that the DOJ has a conflict of interest in an investigation or finds that politics may unduly influence an investigation it conducts, it is required by law to appoint a "special counsel" to oversee the investigation. The appointment of a special counsel is completely at the discretion of the Attorney General. However, this can arguably be swayed by public outcry and Congressional pressure.
While the terms "special counsel," "special prosecutor," and "independent counsel" are often used interchangeably, the positions vary in how they are appointed and the powers they wield. A "special counsel" is appointed by the Attorney General (or the Deputy Attorney General if the Attorney General has recused herself). After the Watergate scandal involving then-President Richard Nixon, Congress passed a law creating "special prosecutors" or "independent counsels" who are appointed by a three-judge panel. In 1999, Congress let this law expire.
A special counsel enjoys the same powers as other federal prosecutors, but has broader discretion over what they share with the DOJ involving their ongoing investigation. The Department of Justice is required to provide the special counsel with a staff. A special counsel has authority to initiate investigations, subpoena records, and ultimately file charges. Once a special counsel's investigation is complete, they submit a confidential report to the Attorney General who then decides whether the special counsel has enough evidence to prosecute the official under investigation. At the end of the investigation, the Attorney General is required to notify Congress of the special counsel's report, but this information does not necessarily become public knowledge.
Two of the most notable special counsel cases in United States history are the Iran Contra investigation and the Whitewater investigation. In the case of the Iran-Contra affair, a special counsel was appointed to investigate allegations that President Reagan and his administration sold weapons to Iran then routed money from that sale to the right-wing "Contra" guerrillas in Nicaragua. A special counsel was appointed and several members of Reagan's administration were charged, but the President himself was never charged.
The Whitewater investigation took place in the 1990's and involved then-President Bill Clinton and First Lady Hillary Clinton and a real estate investment during Clinton's time as governor of the state of Arkansas. At President Clinton's request, Attorney General Janet Reno appointed a "special counsel" to investigate the controversy. Clinton was cleared of wrongdoing, but the case was reopened when it was decided the special counsel had a conflict of interest as he was appointed by Janet Reno, who was appointed by Bill Clinton. A three-judge panel then appointed a special prosecutor, Kenneth Starr, to lead the subsequent investigation. The Clintons were ultimately cleared of wrong doing in the real estate matter, although several of their associates were convicted as a result of the investigation. But that investigation became tangled up in other civil matters that ultimately resulted in President Clinton's impeachment for perjury by the U.S. House of Representatives. He was acquitted by the U.S. Senate and served out his term.
When the current U.S. Attorney General Jeff Sessions recused himself from the current investigation due to his role in the Trump campaign, it became the responsibility of Deputy Attorney General Rod Rosenstein to investigate the ties of the Trump Campaign and Russian officials himself or appoint a special counsel. Late Wednesday May 17th, Rosenstein announced he will turn the reigns of the investigation over to Robert S. Mueller III. Mueller served as Director of the FBI under Presidents Bush and Obama, before which he was a prosecutor for the Department of Justice.