Castellano never stood trial in the Commission case because he was murdered before he came to trial. As Juventus said, "Brasco" mainly helped with evidence against the Bonanno family.
The Commission case was inspired by Rudolph Guiliani's reading of Bonanno's autobiography, "A Man of Honor," and aided by wiretaps and electronic surveillance. Much of the evidence was obtained from a bug in Castellano's home, in which he was heard discussing his business with other Mob bosses. The prosecution was able to convict the Bosses under the RICO Act, by portraying them as members of "The Commission."