That's a great example -- 'Dollar Bill' Jefferson, by an extention of your logic in the Libby case a) hasn't been charged with a crime and b) the only evidence that might be used to charge him with a crime was generated in a 'Sting' that could easily be called entrapment. You should be defending him and questioning his investigation.
Jefferson has been under investigation by the FBI for suspected corruption since March 2005. Since that time, he has been named in the guilty pleas of two associates. On 15 May 2006, Jefferson called a press conference at which he announced that he did not intend to resign, despite expecting to be indicted on corruption charges. On 20 May 2006, Jefferson's Congressional offices were searched by the FBI, "believed to be the first-ever FBI raid on a Congressional office," raising concerns that it could "set a dangerous precedent that could be used by future administrations to intimidate or harass a supposedly coequal branch of the government." See below.
An investigation of Jefferson by various agencies began in mid-2005, after an investor came to authorities. Jefferson is alleged to have received over $400,000 in bribes through a company maintained in the name of his spouse and children. The money came from a tech company named iGate, Inc. of Louisville, Kentucky, and in return, it is alleged, Jefferson would help iGate's business. Jefferson was to persuade the U.S. Army to test iGate's broadband two-way technology and other iGate products; use his efforts to influence, possibly through bribery, high-ranking officials in Nigeria, Ghana, and Cameroon; and meet with personnel of the Export-Import Bank of the United States, in order to facilitate potential financing for iGate business deals in those countries.
 FBI investigation of bribery and fraud
On 30 July 2005, Jefferson was videotaped by the FBI receiving $100,000 worth of $100 bills in a leather briefcase at the Ritz-Carlton hotel in Arlington, Virginia. Jefferson told an investor, Lori Mody, who was wearing a wire, that he would need to give Nigerian Vice President Atiku Abubakar $500,000 "as a motivating factor" to make sure they obtained contracts for iGate and Mody's company in Nigeria. A few days later, on 3 August 2005, FBI agents raided Jefferson's home in Northeast Washington and, as noted in an 83-page affidavit filed to support a subsequent raid on his Congressional office, "found $90,000 of the cash in the freezer, in $10,000 increments wrapped in aluminum foil and stuffed inside frozen-food containers." Serial numbers found on the currency in the freezer matched serial numbers of funds given by the FBI to their informant.
Late in the night of 20 May 2006, FBI agents executed a search warrant at Jefferson's office in the Rayburn House Office Building.
The affidavit used to support these raids included, among other allegations:
The FBI videotaped Jefferson receiving a stock certificate from Mody for a company set up in Nigeria to promote iGate's technology. Jefferson predicted the deal would generate $200 million annually after five years.
Jefferson told Mody that he wanted a similar financial stake in the business in Ghana.
Jefferson sought $10 million in financing from Mody to take over iGate and install "confidants" on the new board. In two payments, Mody wired $89,225 to the ANJ Group LLC, a company controlled by Jefferson's family.
Jefferson lent $4,800 of the money Mody gave him to an unnamed congressional aide. Another $4,900 was given back to the FBI by one of Jefferson's attorneys.
The FBI claims it has uncovered "at least seven other schemes in which Jefferson sought things of value in return for his official acts."
Investigations begin (or should) because of 'probable cause' Denise. The CIA obviously considered the Plame leak to be criminal or they wouldn't have referred it to the FBI for investigation. Certainly the CIA knew whether or not Valerie Wilson was a 'Covert' agent or not.
But in addition to the leaking of a covert agent's identity -- it was also the unauthorized disclosure of classified information (unless of course -- the President had selectively 'declassified' it for political purposes the way he's selectively declassified other information) so both crimes were under investigation.
The knowledge of Armitage as Novak's source though was no reason to stop investigating -- since other reporters were leaked to by other sources and the question of how the classified information came into the possession of those leakers and Armitage is all part of the question to answered in an investigation.
You, like Johnson -- are perfectly at liberty to accuse Jefferson, and even entitled to think he's guilty. Only a court of law has to presume innocence.
If you want to keep this up though -- you too will at some point have to join OJ in his search for the real killers -- since he was acquited in a criminal trial -- but found responsible in a civil trial.
As in that case -- this one will be interesting again when the Wilson's civil case reaches court.