I don't know if Casso ever went into detail with any murders Sammy didn't admit to. He did try to get his own deal, but there were numerous reasons they denied him the deal and gave him 455 years. He admitted to plotting to kill a prosecutor and a judge, he was caught in too many lies, he ran the WitSec unit in Otisville like his own personal fiefdom smuggling in heroin, lobsters, liqour, other drugs and anything he could get his hands on. Bribed prison workers to do it. Had several altercations with Big Sal Micciotta. Had 37 murders or more probably. Plus he flunked the psychiatric exam that said he was a lunatic. They knew they weren't gonna let Casso out of prison and back into society ever again. They just pumped all the info he had and threw him in jail for life which was a very wise thing to do. Casso put his faith in the fact they needed him to put Chin away. He should have used the Mafia Cops as his high card instead.