But Michael German, a former F.B.I. agent who researches national security law at New York University's Brennan Center for Justice, told the Times, "They're manufacturing terrorism cases." In too many instances, he said, "these people are five steps away from being a danger to the United States."

This is not the first time that the F.B.I. has attracted criticism from national-security experts and civil-liberties groups for generating terrorism cases through sting operations and confidential informants. In "The Imam's Curse," published in September, I reported on a Florida family that was accused of providing "material support" to terrorists. In that case, a father, Hafiz Khan, and two of his sons were arrested. The charges against the sons were eventually dropped, but Hafiz Khan was convicted and sentenced to twenty-five years in prison. At Khan's trial, his lawyer, Khurrum Wahid, questioned the reliability of the key informant in the case, David Mahmood Siddiqui. Wahid accused Siddiqui, who'd had periods of unemployment, of lying to authorities because his work as a confidential informant was lucrative. For his role in the case, Siddiqui had received a hundred and twenty-six thousand dollars, plus expenses. But in a subsequent interview with the Associated Press, Siddiqui stood by his testimony and motives: "I did it for the love of my country, not for money."

In an interview with NBC News on Sunday, Seddique Mateen, also known as Mir Siddique, said his son's rampage had "nothing to do with religion."