A special prosecutor generally is a lawyer from outside the government appointed by an attorney general or, in the United States, by Congress to investigate a government official for misconduct while in office. A reasoning for such an appointment is that the governmental branch or agency may have political connections to those it might be asked to investigate. Inherently, this creates a conflict of interest and a solution is to have someone from outside the department lead the investigation. The term "special prosecutor" may have a variety of meanings from one country to the next, from one government branch to the next within the same country, and within different agencies within each government branch. Critics of the use of special prosecutors argue that these investigators act as a "fourth branch" to the government because they are not subject to limitations in spending or have deadlines to meet.
Attorneys in the United States may be appointed/hired particularly or employed generally by different branches of the government to investigate. When appointed/hired particularly by the judicial branch to investigate and, if justified, seek indictments in a particular judicial branch case, the attorney is called special prosecutor. When appointed/hired particularly by a governmental branch or agency to investigate alleged misconduct within that branch or agency, the attorney is called independent counsel.  When employed by the state or political subdivision to assist in a particular judicial branch case when the public interest so requires, the attorney is called special counsel.
On January 3, 1983, the United States federal government substituted the term independent counsel for special prosecutor. Archibald Cox was one of the most notable special prosecutors. However, special prosecutor Archibald Cox today would be called independent counsel Archibald Cox in the United States.
The term is sometimes used as a synonym for independent counsel, but under the former law authorizing the independent counsel, the appointment was made by a special panel of the United States Court of Appeals for the District of Columbia Circuit. The Ethics in Government Act expired in 1999, and was effectively replaced by Department of Justice regulation 28 CFR Part 600, under which Special Counsel Patrick Fitzgerald was appointed to look into the Plame affair.
Special prosecutors may also be used in a state prosecution case when the prosecutor for the local jurisdiction has a conflict of interest in a case or otherwise may desire another attorney to handle a case.
- Black's Law Dictionary (8th ed. 2004) Prosecutor.
- Black's Law Dictionary (8th ed. 2004) Counsel.
- United States Public Law 97-409 (January 3, 1983) as enacted from A bill to change the coverage of officials and the standards for the appointment of a special prosecutor in the special prosecutor provisions of the Ethics in Government Act of 1978, and for other purposes.
- Doyle, James (1977). Not Above the Law: the battles of Watergate prosecutors Cox and Jaworski. New York: William Morrow and Company. ISBN 0-688-03192-7.