According to Jones (2008), 761 newspapers and TV news directors, consisting 38 percent of media outlets in the U.S., received 3062 subpoenas in 2006 and 97 of them sought information of confidential sources . Subpoenas from the state level takes up about 90 percent of all subpoenas (Jones, 2008). Consistent with the study the Reporters Committee for Freedom of the Press conducted in 2001 which showed 54 percent of successful subpoena challenges cited state shield laws, news media in state with shield laws complied with subpoena less often than those from state without shield laws and were more successful in persuading withdrawal of subpoena on the state level (Jones, 2008). With the increasing amount of subpoenas that seek disclosure of confidential sources, state shield laws have become tools of growing importance for reporters to defense themselves, even more effective than the First Amendment privilege they frequently fail to cite.
Maryland passed the first shield law in 1896 and the number of states that enact shield laws has increased gradually since the U.S. Supreme Court’s decision in Branzburg v. Hayes (Digital Media Law Project, n.d.). Currently, 40 out of 50 states along with the District of Columbia have adopted shield law (Mackey, 2011).