[4] Posses served as an informal system of control over local neighborhoods, and their development was connected to political nationalism and Rastafarianism.
[2][6] Applying their unique form of organization, structure, violence, and leadership, posses established a foothold in the illegal drug trade soon after their arrival in the U.S., initially in the importation and sale of marijuana before shifting emphasis to the street-level distribution of cocaine in the early 1980s.
[4] Posses also established working relationships with Colombian cartels, traditional organized crime groups, and West Coast street gangs.
[7] The posses' expansion into territories previously controlled by other drug gangs brought them into conflicts with African-American organized crime groups.
[2] By 1989, posses composed of 10,000 to 20,000 members and associates,[2] most of them illegal aliens,[6] affiliated with approximately 40 gangs operating in 15 metropolitan areas,[6] and controlled an estimated 35 to 40 percent of the crack cocaine market in the U.S.[2] Members of the Shower Posse took up residence in Canada in the 1970s after fleeing Jamaica when the government of Michael Manley took power.
[10] They live a transient lifestyle, incessantly moving between Jamaican diaspora communities in various cities, and often using false identification.
[6][12] During the 1970s, Jamaican drug gangs in the United States were known for trafficking in "Jamaica gold", a sinsemilla strain famed for its potency.
[12][5] James L. Brown, special agent in charge of the Miami district office of the U.S. Bureau of Alcohol, Tobacco and Firearms (ATF), described a "total disregard for human life" as a hallmark of posses.
[14][page needed] The alleged head of the One Order Gang, Andrew "Bun Man" Hope, was murdered in Spanish Town on 8 February 2006, which sparked a riot the following day.