Omertà implies “the categorical prohibition of cooperation with state authorities or reliance on its services, even when one has been victim of a crime.” Even if somebody is convicted for a crime he has not committed, he is supposed to serve the sentence without giving the police any information about the real criminal, even if that criminal has nothing to do with the Mafia himself. Within Mafia culture, breaking the oath of omertà is punishable by death.
A common misconception is that the Mafia created or instituted omertà. In fact, the code was adopted by Sicilians long before the emergence of Cosa Nostra (some observers date it in the 16th century as a way of opposing Spanish rule.) As noted by Harvard anthropologist, Michael Herzfeld, it is also deeply rooted in rural Crete, Greece.
Omertà is a code of silence, according to one of the first Mafia researchers Antonio Cutrera, a former officer of public security, that seals lips of men even in their own defense and even when the accused is innocent of charged crimes. Cutrera quoted a native saying first uttered (so goes the legend) by a wounded man to his assailant: “If I live, I’ll kill you. If I die, I forgive you.”
The suspicion of being a “stool pigeon”, a cascittuni (an informant), constituted the blackest mark against manhood, according to Cutrera. Each individual had the obligation of looking out for his own interests and of proving his manliness by not appealing to legally constituted authority for redress of personal grievances. A wronged person is expected to avenge himself, or find a patron who will see to it that the job is done.
Omertà is based partly on fear and partly on idealism – it is an extreme form of loyalty and solidarity in the face of authority. One of its absolute tenets is that it is deeply demeaning and shameful to betray even one’s deadliest enemy to the authorities. Observers of the mafia debate whether omertà should best be understood as an expression of social consensus surrounding the mafia or whether it is instead a pragmatic response based primarily on fear. The point is succinctly made in a popular Sicilian proverb Cu è surdu, orbu e taci, campa cent'anni 'mpaci ("He who is deaf, blind, and silent will live a hundred years in peace").
In recent years omertà has been broken by mafiosi. Joe Valachi was one of the first persons to betray the omertà when in 1963 he publicly spoke out about the existence of the Mafia and testified before the United States Congress. In Sicily, the phenomenon of pentito (Italian he who has repented), broke omertà in the 1980s.
Among the most famous Mafia pentiti is Tommaso Buscetta, the first important state witness who helped judge Giovanni Falcone to understand the inner workings of Cosa Nostra and described the Sicilian Mafia Commission or Cupola, the leadership of the Sicilian Mafia. (A predecessor, Leonardo Vitale, who gave himself up to the police in 1973, was judged as suffering from 'mental illness' so his testimony led only to the conviction of himself and his uncle.)