A consortium of researchers dedicated to improving the understanding of the human causes and consequences of terrorism

Violent extremism in the U.S.


Part of the National Consortium for the Study of Terrorism and Responses to Terrorism (START), the Global Terrorism Database is an open-source database including information on more than 98,000 terrorist events around the world from 1970 through 2010. It is currently the most comprehensive unclassified database on terrorist events in the world. For each GTD incident, information is available on the date and location of the incident, the weapons used and nature of the target, the number of casualties, and--when identifiable--the group or individual responsible.

Using the database, a team of START researchers found:

  • Between 2000 and 2010 there were 213 terrorist attacks in the United States. Seventeen of these, including four attacks on Sept. 11, 2001, were fatal.
  • Since Sept. 11, 2001, 32 people have been killed in terrorist attacks in the United States. The most lethal attack was the 2009 shooting at Ft. Hood in Killeen, Texas, in which Nidal Hasan killed 13 people.
  • Of the attacks in the United States for which perpetrator information is known (73 percent), the groups most frequently launching completed attacks were the Earth Liberation Front (ELF) and the Animal Liberation Front (ALF). High-profile attacks by individuals affiliated with Tehrik-i-Taliban Pakistan (TTP) and al-Qaida in the Arabian Peninsula (AQAP) were successfully foiled.
  • Thirty-two percent of terrorist attacks in the United States since 2000 have involved individuals with no apparent affiliation to a known extremist group. These individuals included adherents of a range of ideologies, including anti-abortion extremists, environmental extremists, White supremacists, and Islamist extremists.



START's Extremist Crime Database includes a systematic collection of open-source data on non-violent and violent criminal behavior in the United States associated with far-right extremist groups, far-left extremist groups, and al-Qaida-influenced groups.

By developing this database, START researchers have thus far recorded thousands of criminal incidents committed by far-right extremists between 1990 and 2010 and more than one hundred by those inspired by al-Qaida. These crimes range in important ways, such as the level of violence imposed on victims, number of suspects involved and the motivations underlying each incident. For example, far-right extremist crimes include hate crimes, attacks on abortion providers, as well as financial crimes and cases involving illegal firearms and other weapons.


  • More than 345 homicide incidents were committed by at least one far-rightist between 1990 and 2010.
  • Far-rightists killed almost 50 law enforcement officials between 1990 and 2010. These incidents involved federal, state and local police officers, correctional officers, private security guards and one judge.
  • Far-right extremists committed more than 350 "financial schemes" since 1990. Since data collection and coding is ongoing this number will grow.
  • Almost 25 fatal incidents (in which the suspect killed others and/or was killed by police or committed suicide) have been committed by al-Qaida-inspired extremists since 1990. In addition, in this period the Extremist Crime Database identified more than five "honor killing" incidents.
  • Al-Qaida-inspired extremists committed close to 100 "financial schemes" since 1990.
  • Far-right and al-Qaida-inspired extremists in the United States engage in different types of financial schemes, follow distinct modi operandi and are prosecuted for a variety of both financial and non-financial crimes. Despite these differences, a common trend was identified among the cases that have been identified and researched thus far ? the involvement of non-extremist accomplices who provided useful resources for the crime commission process.

Data collection on far-left criminal activity is currently underway.


START's Profiles of Islamic Radicalization in North America Database provides information on 211 individuals known to have radicalized in North America to the point of supporting violence from 1989 to 2011. These homegrown violent extremists started and completed a significant portion of their radicalization in North America, though not all attempted or carried out violence in North America. Each meets at least one of the following criteria: 1) indicted of violence-related crimes, 2) killed as a result of jihadist activities or 3) publicly self-identified as a member of an active jihadist organization.

Using the database, a team of START researchers found:

  • The vast majority of homegrown Islamist extremists (80 percent) began their radicalization after the events of 9/11 and the subsequent Global War on Terrorism.
  • Nearly half of the identified homegrown Islamist extremists (45 percent) come from a middle class background, and the majority (59 percent) are highly rooted in their host society.
  • Although there are considerable missing data about their conversion status, at least 24 percent of the individuals included in this study were converts to Islam.

Support for START's data collection on and analysis of terrorism and extremist violence in the United States is provided by the Science and Technology Directorate, U.S. Department of Homeland Security.