In December, The Washington Post obtained a list of the 361 terrorism-related cases filed by U.S. attorneys' offices in the three years after the Sept. 11, 2001, attacks, and set out to examine each one.

Thirty-one cases were blacked out and could not be evaluated. To assess the others, The Post examined court records, official statements, the Sept. 11 commission report and media accounts, and conducted interviews of prosecutors and defense attorneys. The Justice Department declined to provide additional information on any case.

In The Post's assessment, individual cases were classified as terrorism-related if any supportable allegation of terrorism was made by authorities or could be found through additional investigation. Cases were classified as not related to terrorism if individuals were publicly cleared of connections to terrorism or no link could be found. Except for eight cases ultimately classified as "unknown," The Post accepted the Justice Department's assertion that a case was related to terrorism if circumstances were unclear.

Terrorism- or national-security-related convictions were defined as violations of U.S. terrorism statutes or the International Emergency Economic Powers Act (IEEPA), which gives the president authority to address any unusual and extraordinary threat from outside the country to national security, foreign policy or the economy.