Question: Who investigated whether Lee Harvey Oswald was to blame for the assassination of JFK?
About the article "Assassination of John F. Kennedy", section "Criticism of FBI".

Candidate passages:
The story of Jack Ruby and Lee Harvey Oswald and their involvement in the JFK assassination. 
To support his prosecution of Clay Shaw, Garrison attempted to prove the following:  Clay Shaw was the "Clay Bertrand" who purportedly contacted New Orleans attorney Dean Andrews, to see whether Andrews would be interested in representing Oswald at trial.
Witnesses testified that they saw Oswald with Clay Shaw and David Ferrie in Clinton, Louisiana, just two months before the JFK assassination.
Vernon Bundy testified that he saw Lee Oswald and Clay Shaw together, on the seawall along Lake Pontchartrain in New Orleans during July 1963.
He said that Shaw spoke with Oswald and gave Oswald some money.
Perry Russo testified that Clay Shaw, Oswald, and David Ferrie were present at a party at Ferrie's New Orleans apartment in September 1963, during which they discussed the assassination of JFK, including the "triangulation of crossfire" and the need to have an alibi for that day.  
Ruth Hyde Paine (born September 3, 1932) was a friend of Marina Oswald, who was living with her at the time of the JFK assassination.
According to four government investigations, Lee Harvey Oswald stored the 6.5 mm caliber Carcano rifle that he used to assassinate U.S. President John F. Kennedy in Ruth Paine's garage, unbeknownst to her and her husband, Michael Paine. 
Belin served in the United States Army in Korea and in Japan.
Belin was assistant counsel to the Warren Commission, which investigated President John F. Kennedy's assassination.
He concluded that Lee Harvey Oswald had worked entirely on his own as Kennedy's assassin, which the commission affirmed in its final report.
Belin stood by the findings of the Warren report until his death, and was known to become incensed at any mention of an assassination conspiracy.
As he lay in a coma in his final days, his friends would whisper conspiracy theories about the JFK assassination into his ear to confirm his unconsciousness by his unprecedented lack of response.
Belin wrote two books on the JFK Assassination: "November 22, 1963: You Are the Jury" (1973) and "Final Disclosure: The Full Truth About the Assassination of President Kennedy" (1988).
Belin's former Warren Commission member and then-president Gerald Ford appointed him executive director to the Rockefeller Commission, which investigated CIA activities within the United States. 
JFK conspiracy allegations.
Early comments.
"Give Us This Day", Hunt's book on the Bay of Pigs Invasion, was published late in 1973.
In the book's foreword, he commented on the assassination of President John F. Kennedy as follows:Once again it became fashionable to hold the city of Dallas collectively responsible for his murder.
Still, and let this not be forgotten, Lee Harvey Oswald was a partisan of Fidel Castro, and an admitted Marxist who made desperate efforts to join the Red Revolution in Havana.
In the end, he was an activist for the Fair Play for Cuba Committee.
But for Castro and the Bay of Pigs disaster there would have been no such "Committee."
And perhaps no assassin named Lee Harvey Oswald.