A Hoax or Not? As Threats Rise, Truth Is Elusive.

Reports that people who fabricate terrorist threats have inundated law enforcement officials ever since Sept. 11, 2001. Obligation of law enforcement to investigate each threat; Difficulty in determining the credibility of a threat; Question as to whether the recent threat to the New York subway system was credible; Disagreement between local and federal officials; Details of the threat and New York's response to it; Consideration of various motives for fabricating a threat, including efforts to avoid deportation, emotional and mental instability, and revenge.