This brief document reports on data from the Domestic Terrorism Offender Level Database in order to determine what percentage of the violent extremist population could be “catchable” in the sense that an individual had been in previous contact with a system stakeholder, such as law enforcement or mental health providers, or had been reported to a system stakeholder by a friend or loved one.
This report addresses the relatively high levels of “leakage” associated with acts of public violence, including adolescent-perpetuated mass murders, mass shootings, political and public figure assassinations, and domestic terrorism. The paper discusses efforts to examine pre-attack contacts with system stakeholders such as law enforcement, mental health, and education professionals. The authors refer to a new dataset: the Domestic Terrorism Offender Level database (DTOLD), which includes detailed information on the 320 non-Islamist individuals who carried out terrorist attacks in the U.S. between January 2001 and December 2020. The authors specifically report on their efforts to understand what percentage of that population was known to system stakeholders at some point before they perpetrated their attacks. They report that DTOLD data shows 61.56 percent, or 197 of 320, of the individuals in the dataset as having had contact with a system stakeholder before committing an act of domestic terrorism. They also note that the fact that DTOLD was built on open-source research that leveraged court documents and media reporting, has resulted in some data analysis limitation, and that system stakeholder contact may actually be underestimated.