Copycat crimes

Copycat crimes is a hypothesis based on the social learning model that crimes are replicated and inspired by  knowledge of similar crimes, especially crimes shown widely in the media. However, to date the evidence for the validity of this hypothesis is inconclusive.

Copycat Effect
The copycat effect refers to the tendency of sensational publicity about violent murders or suicides to result in more of the same through imitation. It is also the name of a book on the subject by Loren Coleman.

Newspapers sometimes avoid glorifying vandalism and other petty crimes because of the copycat effect.

Regarding the Virginia Tech shootings, social scientist and author Loren Coleman, The Copycat Effect (New York: Paraview Pocket-Simon and Schuster, 2004, ISBN 0-7434-8223-9), has written in some detail in his same-named blog and been extensively quoted by the media regarding the impact that the wall-to-wall coverage had in framing Cho's attack, and in the copycats in its wake.

Research on etiology of copycat crimes
It has been shown that most of the persons who do mimic crimes seen in the media (especially news and crime movies) have in most cases prior criminal records, prior severe mental health problems or histories of violence suggesting that the effect of the media is indirect (more affecting criminal behaviour) rather than direct (directly affecting the number of criminals). It has also been seen that there is certain small population of people who are at more risk for harmful media influences than the general audience.

Statistics

 * United States cities by crime rate