Closing arguments in the Jose Padilla trial are set to begin Aug. 13 in Miami. Padilla is on trial for allegedly supporting plots to carry out jihadist attacks in the United States. He is also associated with an alleged plot to detonate a "dirty bomb," or radiological dispersal device (RDD), inside the United States as part of a jihadist attack. On Aug. 10, an Israeli-based Internet media outlet reported the threat of an impending dirty bomb attack on the United States. The report cited statements posted on jihadist Web sites regarding an attack "by means of trucks loaded with radioactive material against America's biggest city and financial nerve center." This report prompted the New York Police Department (NYPD) to take security precautions, including setting up vehicle checkpoints near the financial district in Lower Manhattan. The next day, after it became clear that the report of the threat was not entirely reliable, the NYPD stood down. The issue of RDDs — devices containing a small amount of radioactive material meant to be dispersed by a conventional explosion — surfaces periodically. Spikes in interest usually coincide with events in the Padilla trial, statements by jihadist groups or rumors; the most recent peak in public interest was in the fall of 2006 and was spurred by rumors of al Qaeda operatives and materials coming into the United States via Mexican smuggling routes. The approaching anniversary of the 9/11 attacks, along with the closing arguments in the Padilla trial, are likely to garner more media attention for the RDD issue — even though Padilla is being tried on other charges relating to the support of terrorist activities, rather than his connection to the alleged RDD plot. His prior association with such a plot will help draw public attention to RDD threats. Though the threat of a dirty bomb attack is valid and should be taken seriously, the statements that sparked the latest warning are not exactly realistic. Jihadist Web sites frequently include grandiose threats about RDD attacks, sometimes referring to an "American Hiroshima." This does not mean the jihadists can actually carry out such an attack. RDDs can be constructed with any amount of radioactive material — usually measured in grams, not thousands of pounds. Because such material is not particularly difficult to obtain, it might seem surprising that a jihadist cell has not carried out an RDD attack. However, it would be impractical, if not impossible, for a jihadist cell to obtain the "truckloads" of radioactive material referred to in the most recent dirty bomb threat. Furthermore, in an RDD attack more casualties would result from the conventional explosion needed to disperse the radioactive material than from any radiation dispersed. Serious jihadists have probably realized that an RDD attack would not be worth the risk and likely would not be as effective as a conventional attack. The statements that caused the latest interest in RDD attack represent jihadist wishful thinking. One poster on the jihadist Web site speculated that "The attack, with Allah's help, will cause an economic meltdown, many dead, and a financial crisis on a scale that compels the United States to pull its military forces out of many parts of the world, including Iraq, for lack of any other way of cutting down costs." This is not realistic. While the actual physical damage and casualties caused by a dirty bomb attack in New York City's financial center would not parallel that caused on 9/11, it would certainly cause political, social and economic chaos, at least for the short term. Because of this, RDDs are considered more "weapons of mass disruption" than "weapons of mass destruction." Despite the damage such an attack could do to the U.S. economy, Washington's policy in places like Iraq and Afghanistan would not reverse (and could, in fact, accelerate). Though an RDD attack in the United States would not cause too much physical and economic damage, it would be a huge victory for the jihadist agenda. Whether such an attack is carried out by a grassroots cell originating in the United States or an actual al Qaeda cell, it would be as huge a psychological and propaganda victory for the jihadists as the Doolittle Raid was to the Allies in World War II.