Border Crossings and Terrorist Attacks in the United States: Lessons for Protecting Against Dangerous Entrants

Project Details


The research conducted for this project was motivated by an effort to improve understanding of the degree to which individuals who have engaged in terrorist activity in the United States have crossed in and out of the country during planning and in the wake of illegal and/or violent activities. With the September 11, 2001 attacks as a robust demonstration of the damage that can be inflicted by individuals with vicious intent who gain access to the country, the research team sought to determine to what degree the general travel patterns of the 9/11 attackers were common to others who have attacked the United States and how knowledge gained about the dynamics of such individuals in the past might inform border security personnel and practices today.

This data collection and analysis effort was framed in accordance with insights about the dynamics of border crossing from researchers from the University of Arizona affiliated with the BORDERS Center who, in turn, will develop guidance for screening potential terrorists at the border based on what has been learned from analyses of previous terrorist attacks. The project, funded through a Multi-Disciplinary, Multi-Institutional Research award from DHS's Office of University Programs, involves researchers from START--including Gary LaFree and Kathleen Smarick (University of Maryland) and Brent Smith and Jackson Cothren at the Terrorism Research Center (University of Arkansas) and a research team from the University of Arizona's National Center for Border Security and Immigration (BORDERS) COE, including Jay Nunamaker, Elyse Golob, and Aaron Elkins.

Primary Findings:

Fieldwork at select ports of entry (POEs) led the research team to conclude that the primary and overwhelming concern of screening agents at POEs remains the immigration status of entrants. Their processes are directly informed by information on specific passengers from the National Targeting Center but the overall screening process is not focused on or built around identifying individuals who may have intentions of plotting violent attacks against the United States. The question remained, however, to what degree individuals engaged in terrorist plots have crossed in and out of the United States and whether they have been successful at evading detection at POEs. Information gained on this could inform the degree to which border officials allocate resources with respect to the counterterrorism mission.

Based on information about individuals in the United States who have been charged with Federal terrorism crimes between 1980 and 2004, the research team identified 264 indicted individuals who had been involved in 221 border crossings at U.S. POEs according to public court documents.  These identified border crossings served as the building blocks for the U.S. Terrorism Border Crossing (USTBC) dataset. This dataset includes information on what POEs were involved in a specific border crossing, the origin and final destination of the crosser, his/her citizenship and immigration status, as well as demographic and background information on the crosser.

Analyses of these newly collected data revealed trends involved in these border crossings by individuals indicted on federal terrorism charges: The border crossers were most often U.S. citizens entering back into the United States, most often via an airport (rather than a seaport or a land port of entry).  Almost all were male, and a large majority were married. There was notable variation in the origins of travel for these border crossers, with trips originating all around the world, and some—but only a minority—had previous arrests, according to U.S. court documents.


To supplement the historical, aggregated data, this project included a series of case studies examining how potential and actual terrorists have exploited U.S. borders. The four cases examined in detail were Ahmed Ressam (Millenium Bomber), Ghazi Ibrahim Abu Mezer, the 1993 World Trade Center Bombers and the North Carolina cigarette smuggling group affiliated with Hezbollah. Natural comparisons emerged between Ressam and Abu Mezer: As discussed in detail in the case studies, both were entries into the United States in the state of Washington from Canada via a land or port crossing (as opposed to entry at an airport), neither crossing was legal, both were clearly tied to terrorist activity, they occurred within a three-year period, and both individuals had a criminal record. The major difference is that one managed to cross successfully (Abu Mezer), while the other (Ressam) did not, although the former was stopped repeatedly by astute border agents.


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