I am fully aware that this was not a trial. I understand that it was a hearing. But if the Committee was willing to put Hagen's face up on a mob family tree crime board, than surely they would have loved to have a witness who could possibly implicate both The Don and his Consigliere. Both Michael and his lawyer. And therefore by the committee including Hagen on their board as a member of the family, a high ranking figure right under the head of the family, it is quite obvious that they would have loved to take him down along with Michael.

Taking Hagen down along with Michael by having corroborating testimony from two underlings would have crippled Michael in an eventual trial in a court of law.

But I don't believe that Cicci flipped because if he did, he would have implicated Frankie and would have corroborated the committee's assertion that Tom Hagen was indeed a big shot in the Corleone crime family. He would have told the committee about how Tom Hagen was involved in the set up that led to the demise of Tessio. Michael would have taken revenge on Cicci just as he did on all those who he thought betrayed him or were a threat to him. But Michael did not include Cicci in those plans because Cicci did not turn rat.

So while everything that you say is true, the reply still does not address the bottom line question of whether Willie Cicci had turned rat or not.