I was trying to rewrite the informant section of Wikipedia's Anthony Casso article, but I need some clarification on something.

From a Google News search, and Five Families, it appears as though Casso never made accusations against Gravano and D'Arco before he sent that letter during Gigante's trial.

It just seems weird to me that he wouldn't be called to testify if he hadn't already made clear his intentions to discredit the two main witnesses. Any other sources to confirm this?