Forensic investigators of the Boston Marathon bombing are gathering clues to the makeup — and perhaps even the maker — of the bombs that killed three and injured about 180. Read related article.

Sources: “Practical Bomb Scene Investigation,” by James T. Thurman; FBI;; Homeland Security Department CORRECTION: A previous version of this graphic cited whistleblowers and concerned scientists for the assertion that the National Security Agency “amasses everyone’s cellphone calls and online activity.” In fact, the NSA may not intercept Americans’ phone calls and emails, or any electronic communications on U.S. soil, without court oversight | Patterson Clark and Alberto Cuadra/The Washington Post April 17, 2013
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