Yates is right. Casso did involve Gravano and the fact that he lied about murders that he himself ordered and committed and said that Gravano tried to pin those murders on Gotti, by claiming Gotti ordered them. He also told the feds that he knew for a fact that Gravano lied about not touching drugs and claimed Gravano tried to sell him kilos of cocaine. That wasnt the sole reason for them cutting Casso's deal though . But I think it was Selwyn Raab in "Five Families" who claimed that the feds wouldnt give that testimony any credence because it wouldve given Gotti a chance for appeal.