In the years since the 9/11 attacks, the individual perpetrators of these and similar crimes have scarcely been studied although, since July 2015 alone, Islamists have murdered at least 92 people in the United States. Many others have been convicted—or are being prosecuted—for joining or trying to join the self-named Islamic State (ISIS). Analysis of all mass murderers' motivations, ideologies, and radicalization is crucial, but it has been neglected for offenders claiming to act in the name of Islam. However, a data-rich study by sociology professor Charles Kurzman of the University of North Carolina at Chapel Hill offers a window into Islamist terrorist radicalization.
Overlooking Islamic Radicalization
Understanding who radicalizes and why they do is a crucial undertaking. "If you know yourself but not the enemy," Sun Tzu famously wrote in the Art of War, "for every victory gained you will also suffer a defeat." Likewise in criminal justice, understanding offenders helps prevent crime.
The idea is generally noncontroversial. After the attack on Columbine High School in 1999, for instance, the federal government emphasized the importance of pre-incident indicators in its report about preventing school shootings:
The focus of the Safe School Initiative was on examining the thinking, planning, and other behaviors engaged in by students who carried out school attacks. Particular attention was given to identifying pre-attack behaviors and communications that might be detectable—or "knowable"—and could help in preventing some future attacks.
Mainstream reporters have since published a raft of articles purporting to identify the warning signs of potential school shooters before they take the last step to violence. Likewise, calls to understand the process of radicalization to mass murder followed the October 2017 Las Vegas shooting while, after the October 2018 massacre of eleven members of Pittsburgh's Jewish community, journalists across the country ruminated about the killer's white supremacist motives and ideology.
Yet similar calls to identify the warning signs of radicalization to Islamist terrorism have been condemned as "Islamophobic" and shut down. Retired Department of Homeland Security analyst Philip Haney revealed that the Obama administration ended his investigations into extremist Islamic groups, ostensibly due to violations of civil liberties. Worse, he argued, the administration "erased the dots we were diligently connecting." This action appears to have chilled research efforts. For example, the 2016 settlement of a lawsuit arising from the New York Police Department's Muslim surveillance activities required NYPD to remove a 2007 report, titled "Radicalization in the West: The Homegrown Threat," from its website. In a report to the FBI director, the 9/11 Review Commission noted:
Senators Lieberman and Collins, in their committee report, found that the FBI's handling of information that it had concerning [Army Major and Ft. Hood shooter Nidal] Hasan was "impeded by division among its field offices, insufficient use of intelligence analysis, and outdated tradecraft." In addition, they found that the inquiry into Hasan was 'focused on the narrow question of whether he was engaged in terrorist activities and not whether he was radicalizing to violent Islamist extremism and could thus become a threat."
What do we know about the perpetrators of Islamist attacks? Very little, according to a study of the literature. According to Sarah Desmarais of North Carolina State University, "over the past quarter century, there have been six research articles that are useful in identifying someone who is likely to engage in terrorism. And the quality of those six studies is variable."
The Kurzman Database
In January 2017, the Triangle Center on Terrorism and Homeland Security published the Kurzman database, listing 414 people convicted of engaging in or planning Islamist violence against Americans since 9/11. The spreadsheet includes criteria such as the offenders' age, ethnicity, citizenship, education level, and whether they are converts, previously incarcerated, or mentally ill.
Kurzman barely analyzed his own data and does not seem to grasp its full implications.
Kurzman, however, barely analyzed his own data and does not seem to grasp its full implications. His report appears designed primarily to criticize then president-elect Donald Trump. "Few of these individuals ... had family backgrounds from the seven countries reportedly designated by the Trump administration for temporary immigration ban," he writes, adding that "the children of immigrants do not appear to be over-represented among Muslim-Americans involved with violent extremism."
But, Kurzman has a history of minimizing the dangers of Islamist violence. He argued in a USA Today interview that "the wall-to-wall coverage—and our 'zero-tolerance' approach to terror—is disproportional compared to other kinds of violence in America." He has repeatedly argued that the number of Muslims involved in terrorism is disproportionately small.
His dataset may also be incomplete. It includes information on 414 individuals, yet the U.S. Department of Justice convicted at least 500 since 9/11 and prosecuted 711 through mid-2016. Mother Jones kept a now-defunct online database that included 508 prosecuted in the 10 years after 9/11. The 414 in the Triangle database appear to represent little more than half the number of Islamist offenders between September 2001 and January 2017.
Nevertheless, Kurzman's information about violent Islamists is a good starting point for a data-driven statistical analysis of radicalization.
Islam or Islamism?
A 2017 French study suggests that, at least in France, religious beliefs are a strong driver of radicalization. Middle East Forum president Daniel Pipes, meanwhile, has argued that the political-religious ideology known as Islamism, more than traditional Islam itself, is the problem. Islamism poses as a fundamentalist, back-to-basics movement and claims to speak for all of Islam, but it is in fact a utopian ideology that borrows from other twentieth century "-isms" such as Marxism and fascism. Kurzman does not refer to Islamist ideology but to "Muslim extremists" (and, rarely, to "Islamist terrorists") and argues that surprisingly few Muslims turn to or support terrorism. He does not distinguish between Islam and Islamism, and he denies that Islam is the problem, contrary to others who insist that it is.
If traditional Islam is to blame, it could be expected that the overwhelming majority of terrorists consist of traditionally-observant Muslims. If the problem is not traditional Islam but rather a non-traditional ideology building on Islam, terrorists might be expected to come disproportionately from those who know the least about the religion, especially those who were not raised in observant households.
Kurzman's data can partially resolve this dispute about who radicalizes and why. The database does not include details about the perpetrators' religious background, but it does note whether the offenders converted, and this information may serve as a proxy for the answer. If converts are disproportionately represented, it would suggest the problem is less traditional Islam and more Islamism.
The Triangle database also identifies perpetrators' ages. Violent crime is most often committed by young men. Does the same apply to Islamist terrorists?
Attacks were committed by terrorists who appear to have been radicalized in prison.
Where and how perpetrators become radicalized is another concern. If the motivation is based on traditional Islam, one would expect radicalization to occur in the home or the mosque attended by perpetrators in their youth. If a non-traditional Islamist ideology is to blame, and the parents adhere to that ideology, one would also expect radicalization to occur in the home. Otherwise radicalization should be expected to develop elsewhere at least some of the time. The database does not specifically address this question, but it does note whether perpetrators were imprisoned before committing their offenses. Some well-publicized attacks were committed by terrorists who appear to have been radicalized in prison, including Westminster attacker Khalid Masood and Paris attackers Cherif Kouachi and Amedy Coulibaly.
There are indications that radicalization is also taking place in American prisons. If terrorists' prior incarceration rates exceed the norm, it may suggest that many of them were radicalized in prison.
Predominant Ethnic Subgroups
Overall trends can be discerned most easily by combining several ethnic and national groupings, especially since comparative data is often broken down by ethnicity and race. For instance, Kurzman's data identifies perpetrators' nationalities including Egyptian, Yemeni, Saudi, Qatari, Algerian, and Moroccan. For the present analysis, these are combined as "Arab," the largest ethnicity represented in the article, with 89 offenders, or 21.5 percent of the database although only 14 percent of American Muslims are Arab. This is followed by non-African blacks with 74 (18 percent); whites with 68 (16 percent); black Africans with 61 (15 percent, although it is estimated that only 5 percent of American Muslims are from sub-Saharan Africa); and South Asians with 49 (12 percent, a smaller percentage than the 20 percent of American Muslims of South Asian ancestry). Together, these five subgroups account for 341 (82 percent) of the 414 offenders.
The black African category includes people from sub-Saharan Africa and first-generation descendants of immigrants from the region. For example, several Somali-American offenders are native-born U.S. citizens but are classified as black Africans since they are from immigrant communities.
Caucasus and Central Asian ethnicities are grouped separately from "white" under a "former USSR" category, which includes 2 Uzbeks; 1 Kazakh; and Dzhokhar and Tamerlan Tsarnaev, the Chechen-American brothers who committed the Boston Marathon bombing in 2013. Because this subgroup is so small—only five offenders—it does not figure in the analysis.
Based on these groupings, the Triangle database reveals the following regarding the offenders' religious background, age, and prior incarceration history.
Roughly 35.5 percent of offenders in the database (147 out of 414) converted to Islam—nearly twice the rate of converts in the American Muslim population as a whole (20 percent). All of the 49 South Asians in the study were born Muslim while 86 of the 89 Arabs (96.6 percent) and 58 of the 61 black African offenders (95 percent) were born Muslim. By contrast, only 6 of the 74 non-African black offenders (8 percent) were born Muslim, as were 19 (28 percent) of the 68 white offenders.
Offenders in the database converted to Islam at nearly twice the rate as in the American Muslim population as a whole.
Interestingly, converts may have been more disproportionately represented among Islamist terrorists in Europe. According to a 2011 study, "European converts have participated in most terrorist plots and actual attacks that have taken place on European soil since 9/11" although they made up only 2 percent of Europe's Muslim population.
There is anecdotal evidence that several perpetrators born as Muslims lived very secular lives before committing their offenses, including 9/11 hijacker Ziad Jarrah, would-be Times Square bomber Faisal Shahzad, British terror-radicalizer Mustafa Kamel Mustafa (a.k.a. Abu Hamza al-Masri), and Mumbai massacre planner David Headley (a.k.a. Daood Gilani). In a sense, they, too, are converts since the ideology fulfilled them in ways their secular lives did not.
Of the 341 offenders from the five ethnicities noted above, the database identified age at the time of the attack or arrest for 319 offenders. Their average age was 27.2 years.
For the various groups, the ages of all offenders from each group whose ages were known were averaged: Black African offenders were the youngest with an average age of 22.5. Next came Arab offenders (average age 26.9) followed by South Asian offenders (fractionally higher at 27.1). White offenders were a bit older with an average age of 28.1. Black non-African offenders were the oldest at 30.4.
The average age is a bit older than usual for criminal conduct in general. By the age of 26, most offenders have aged out of crime, which is why the U.S. Parole Commission's Salient Factor Score measuring the likelihood of recidivism assigns a better score to offenders who were 26 or older when they committed their crimes. The average age of Islamist terrorists, however, is just over 27. Among those subgroups most likely to have converted, the average age was even higher, with white offenders averaging 28.1 and non-African black offenders 30.4.
Information on prior imprisonment for nearly one in five of the individuals reviewed in the study was unavailable, so one must be especially cautious in forming conclusions. Nevertheless, of the 341 offenders from the five subgroups studied, at least 54 (15.8 percent) were previously incarcerated. The subgroups known to have significant prior incarceration rates are whites (24 percent) and non-African blacks (36 percent), well above those for the general public.
According to the last Bureau of Justice Statistics report on the subject, from 2003, the prior incarceration rate for all males aged 25-34 was 6 percent, and for all males 18-24, it was 2.7 percent. The rates were 2.8 percent for white American males and 20.4 percent for black American males ages 25-34 although black incarceration rates have since fallen. Notably these are the same subgroups from which substantial numbers of converts were drawn.
The unusually high incarceration rates of Islamist offenders compared with the U.S. population as a whole is consistent with the wider Muslim overrepresentation in American prisons (or in European prisons, which seem to be hotbeds of radicalization).
The possibility that significant numbers of Islamist terrorists may be radicalizing in prison before committing jihadist crimes adds to the urgency of America's need to identify whether and to what extent its own prisons are breeding grounds for terrorists, both to prevent radicalization and to develop effective rehabilitative programs for Islamist offenders. Judging by the unusually high proportion of converts among the terrorists in Kurzman's dataset compared to the U.S. Muslim population in general, together with unusually high incarceration rates among the terrorists from these groups, there is little room for complacency in this respect.
The evidence suggests the United States may have a problem with converts to a violent ideology they identify as authentic Islam. Many of these appear to have converted in prison while others were radicalized by people who themselves had been radicalized in prison, or by influential preachers such as Yemeni-American imam Anwar Awlaki, or by the Internet through such jihadist organizations as the New York-based Revolution Muslim.
While the data here may be insufficient to draw firm conclusions, it nevertheless suffices to identify alarming patterns about the motivating ideologies and radicalization of young Muslims, especially when these patterns appear to dovetail with European developments. The U.S. administration must comprehend that understanding the ideology behind terror in the name of Islam is crucial to its defeat.
Johanna E. Markind is an attorney and writer who has worked for the U.S. Department of Justice and in private practice. She has been published in The Wall Street Journal and elsewhere.
 See ABC News, July 21, 2015; Los Angeles Times, Dec. 6, 2015; Chicago Tribune, June 12, 2016; CBS News, Sept. 26, 2016; Newsweek, Jan. 17, 2017; Fresno (Calif.) Bee, Apr. 18, 2017; ABC Action News, May 19, 2017; "Sayfullo Saipov Charged with Terrorism and Murder in Aid of Racketeering in Connection with Lower Manhattan Truck Attack," U.S. Department of Justice, Nov. 21, 2017; Palm Beach Post, Mar. 23, 2018.
 FBI Records: The Vault: Criminal Profiling, Federal Bureau of Investigation (FBI), U.S. Department of Justice, Washington, D.C.; John E. Douglas and Alan E. Burgess, "Criminal Profiling: A Viable Investigative Tool against Violent Crime," FBI Law Enforcement Bulletin, Dec. 1986.
 Bryan Vossekuil et al., The Final Report and Findings of the Safe School Initiative: Implications for the Prevention of School Attacks in the United States (Washington, D.C.: U.S. Secret Service and U.S. Department of Justice, June 2004).
 Abby Ohlheiser, "The Associated Press's New Definition of 'Islamist,'" Slate (New York and Washington, D.C.), Apr. 5, 2013.
 Philip Haney, "Administration nixed probe into Southern California jihadists," The Hill (Washington, D.C.), Dec. 16, 2015.
 Commissioners Bruce Hoffman, Edwin Meese, III, and Timothy J. Roemer, "The FBI: Protecting the Homeland in the 21st Century: Report of the Congressionally-directed 9/11 Review Commission to the Director of the Federal Bureau of Investigation," Washington, D.C., Mar. 2015.
 Sarah Desmarais and Matt Shipman, "Study: There Is Almost No Research on What Distinguishes Potential Terrorists," North Carolina State News, Sept. 25, 2017. For the study see, Sarah L. Desmarais et al., "The State of Scientific Knowledge Regarding Factors Associated with Terrorism," Journal of Threat Assessment and Management, Sept. 14, 2017.
 Charles Kurzman, "Muslim-American Involvement with Violent Extremism, 2016," Triangle Center on Terrorism and Homeland Security at Duke University, Jan. 26, 2017. Since this article was originally drafted, Kurzman updated his data set with information for additional individuals at http://kurzman.unc.edu/muslim-american-terrorism/annual-report/.
 Kurzman, "Muslim-American Involvement with Violent Extremism, 2016," p. 2. The seven countries are Iran, Libya, Somalia, Syria, Yemen, North Korea, and Venezuela.
 Greg Toppo, "Expert: Terrorism frightens us 'far out of proportion' to actual risk," USA Today, Sept. 21, 2016.
 Religion News Service, Journalism School, University of Missouri, Feb. 2, 2016; Charles Kurzman, The Missing Martyrs: Why There Are So Few Muslim Terrorists (New York: Oxford University Press, 2011).
 "Remarks of the Attorney General on the 16th Anniversary of the September 11 Terrorist Attacks," U.S. Department of Justice, Washington, D.C., Sept. 11, 2017.
 Database at http://www.motherjones.com/fbi-terrorist was removed. See, also, "Terror Trials by the Numbers: Stings, informants, and underwear bombs: Digging through the data from federal terrorism cases," Mother Jones, Sept./Oct. 2011.
 Fabien Trécourt, "Une vaste enquête sur la radicalité chez les lycéens," Journal of Centre Nationnal de la Recherche Scientifique, Mar. 20, 2017; Yves Mamou, "France: The Ideology of Islamic Victimization," Gatestone Institute, New York, May 18, 2017.
 Daniel Pipes, "Distinguishing between Islam and Islamism," Center for Strategic and International Studies, Washington, D.C., June 30, 1998; Pipes, "Islam vs. Islamism," The Washington Times, May 13, 2013.
 Kurzman, "Muslim-American Involvement with Violent Extremism, 2016," p.7; Charles Kurzman and David Schanzer, "The Growing Right-Wing Terror Threat," The New York Times, June 16, 2015.
 Terry McDermott, "Charles Kurzman's 'The Missing Martyrs: Why There Are So Few Muslim Terrorists,'" The Washington Post, Aug. 18, 2011.
 Christine Douglass-Williams, "Robert Spencer Exposes Islam's Problematic History," Mackenzie Institute, Toronto, Can., Aug. 31, 2018.
 Linda Drazga Maxfield et al., "A Comparison of the Federal Sentencing Guidelines Criminal History Category and the U.S. Parole Commission Salient Factor Score," Research Series on the Recidivism of Federal Guideline Offenders, United States Sentencing Commission, Washington, D.C., Jan. 4, 2005, pp. 8, 13-15; Christopher Ingraham, "10 percent of the population commits 63 percent of the homicide," The Washington Post, June 18, 2015.
 The Telegraph (London), Mar. 24, 2017, Aug. 20, 2017; IPT News, The Investigative Project on Terrorism, Aug. 23, 2017; The Washington Post, July 26, 2018; Jawad Iqbal, "We need to know more about spread of Islam in prisons," The Times (London), Oct. 17, 2018.
 Patrick T. Dunleavy, The Fertile Soil of Jihad: Terrorism's Prison Connection (Washington, D.C.: Potomac Books, 2011), pp. xiii-xiv; Sen. Charles E. Grassley, chairman, Senate Committee on the Judiciary, to Honorable Thomas R. Kane, acting director of the Bureau of Prisons, Letter dated Jan. 27, 2016, Chuck Grassley website.
 "Muslim Americans: No Signs of Growth in Alienation or Support for Extremism: Section 2: Religious Beliefs and Practices," Pew Research Center, Washington, D.C., Aug. 2011.
 "9-11 Commission Report, §5, Al Qaeda Aims at the American Homeland," National Commission on Terrorist Attacks upon the United States, July 22, 2004; "Chronology of Sept. 11 terror plot," Frontline, Public Broadcasting Service (PBS).
 U.S. Parole Commission Rules and Procedures Manual, U.S. Department of Justice, p. 72.
 Thomas P. Bonczar, "Prevalence of Imprisonment in the U.S. Population, 1974-2001," Bureau of Justice Statistics, Office of Justice Programs, U.S. Department of Justice, Washington, D.C., Report No. NCJ 197976, Aug. 17, 2003, p. 6.
 Glenn Kessler, "The stale statistic that one in three black males 'born today' will end up in jail," The Washington Post, June 16, 2015.
 "Religion in Prisons: A 50-State Survey of Prison Chaplains," Pew Research Center/Pew Forum on Religion and Public Life, Washington, D.C., Mar. 22, 2012, p. 23; "Table: Muslim Population by Country," Pew, Jan. 27, 2011.
 BBC News, Mar. 11, 2015; George Packer, "The Other France: Are the suburbs of Paris incubators of terrorism?" The New Yorker, Aug. 31, 2015; Scott Sayare, "The Ultimate Terrorist Factory: Are French prisons incubating extremism?" Harper's Magazine, Jan. 2016; "Regional Symposium to Combat Recruitment and Radicalization to Violence in Prisons," U.S. Department of State, Washington, D.C., Apr. 26, 2017.
 Donald Van Duyn, deputy assistant director, Counterterrorism Division, FBI, testimony before the Senate Committee on Homeland Security and Governmental Affairs and Related Agencies, Washington, D.C., Sept. 19, 2006; Patrick Dunleavy, "U.S. Ill Prepared for Convicted Jihadis Ending Their Prison Sentences," Investigative Project on Terrorism, Feb. 8, 2017; The Wall Street Journal, May 23, 2019; Chris Costa, former senior director for counterterrorism, National Security Council, and Mitchell D. Silber, former director of intelligence analysis, New York City Police Department, comments in "Countering Radicalization and Terrorist Recruitment," hosted by International Spy Museum, Mar. 18, 2019, min. 39:00-42:00.
 Jesse Morton and Mitchell Silber, From Revolution Muslim to Islamic State: An Inside Look at the American Roots of ISIS' Virtual Caliphate, New America (Washington, D.C.), June 4, 2018; "The Revolution Method Proves Its Success," in From Revolution Muslim to Islamic State.