All signs indicate that the mafia ritual is practiced for purely internal reasons. For over one hundred years the ceremony has undergone almost no modification at all. If it existed merely to impress others, modifications would be expected in response to changes in fashion and taste. So what internal function does the ritual serve? One hypothesis is that it may set the seal on a contract which cannot be ratified in the conventional way: shaking hands is a weak gesture which does not capture the imagination of recruits and cannot be expected to deter opportunistic behavior in an illegal world; scribbling one's name at the bottom of a written document, itself a ritual act binding parties in ordinary transactions, has the additional disadvantage of leaving evidence behind. Hence this most prosaic protection deal is transmuted into a permanent bond by means of a concentrated symbolic act.

XREF: Relates to symbolic interaction and ritual theory, plus how institutions create binding commitments through non-legal means.

Diego Gambetta, The Sicilian Mafia The Busi…, loc. 402