There were four men who waked away relatively unscathed from the Becker-Rosenthal Affair, even though they were arguably most complicit in the murder. All four took a plea deal in exchange for their perjured testimony on the stand against Lt. Becker and the four "Shooters" from the Lenox Gang.
Jack Rose, Harry Vallon, Sam Schepps, and Bridgey Webber were all deeply involved in the Tenderloin gambling and prostitution scene. They all knew one another from childhood, and would do anything and everything to save themselves and their friends, even at the cost of condemning others to an unjust execution.
In Chapter 6, we hit our point of frustration and futility with this story, while discussing these four stool pigeons.