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Bombing Alone: Tracing the Motivations and Antecedent Behaviors of Lone-Actor Terrorists

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This article analyzes the sociodemographic network characteristics and antecedent behaviors of 119 lone-actor terrorists. This marks a departure from existing analyses by largely focusing upon behavioral aspects of each offender. This article also examines whether lone-actor terrorists differ based on their ideologies or network connectivity. The analysis leads to seven conclusions. There was no uniform profile identified. In the time leading up to most lone-actor terrorist events, other people generally knew about the offender's grievance, extremist ideology, views, and/or intent to engage in violence. A wide range of activities and experiences preceded lone actors' plots or events. Many but not all lone-actor terrorists were socially isolated. Lone-actor terrorists regularly engaged in a detectable and observable range of activities with a wider pressure group, social movement, or terrorist organization. Lone-actor terrorist events were rarely sudden and impulsive. There were distinguishable behavioral differences between subgroups. The implications for policy conclude this article.
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PAPER
PSYCHIATRY & BEHAVIORAL SCIENCES
Paul Gill,
1
Ph.D.; John Horgan,
2
Ph.D.; and Paige Deckert,
3
M.S., A.B.D.
Bombing Alone: Tracing the Motivations and
Antecedent Behaviors of Lone-Actor
Terrorists*
,,
ABSTRACT: This article analyzes the sociodemographic network characteristics and antecedent behaviors of 119 lone-actor terrorists. This
marks a departure from existing analyses by largely focusing upon behavioral aspects of each offender. This article also examines whether
lone-actor terrorists differ based on their ideologies or network connectivity. The analysis leads to seven conclusions. There was no uniform
profile identified. In the time leading up to most lone-actor terrorist events, other people generally knew about the offenders grievance, extrem-
ist ideology, views, and/or intent to engage in violence. A wide range of activities and experiences preceded lone actors plots or events. Many
but not all lone-actor terrorists were socially isolated. Lone-actor terrorists regularly engaged in a detectable and observable range of activities
with a wider pressure group, social movement, or terrorist organization. Lone-actor terrorist events were rarely sudden and impulsive. There
were distinguishable behavioral differences between subgroups. The implications for policy conclude this article.
KEYWORDS: forensic science, terrorism, terrorist behavior, lone-actor terrorism, lone-wolf terrorism, typology, motivation
This article analyzes the sociodemographic network character-
istics and antecedent behaviors of lone-actor terrorists leading up
to their planning or conducting a terrorist event. Previous
research has examined the strategic qualities of lone-actor terror-
ists (CTA, 2011), perceptions of the threat posed by lone actors
(1), the narratives that promote lone-actor terrorist events (2),
lone-actor terrorist attack characteristics and impacts (3), and
individual case studies (for example [46]). This research marks
a departure from that domain because it largely focuses upon
behavioral aspects of each offender.
This paper also examines differences between subgroups of
lone-actor terrorists. In the limited literature that currently exists,
offenders tend to be depicted in a binary fashion; subjects either
are or are not a lone-actor terrorist. Lone-actor terrorists are
therefore typically treated in a homogeneous manner, an exception
being Pantuccis (7) typology. Anecdotally, however, there are a
number of easily distinguishable differences in lone-actor terror-
ists characteristics, behaviors, and connectivity with other groups.
Specifically, this article examines whether the characteristics and
behaviors of lone-actor terrorists differ based on their ideologies,
network connectivity, or level of operational success.
The questions explored in this study are the following:
What, if any, demographic characteristics define lone actors?
What ideologies are associated with lone-actor terrorist
events?
To what extent are close friends and family or wider
networks of coconspirators typically aware of the lone-actor
terrorists intent to engage in terrorist-related offenses?
To what extent are coconspirators typically involved in the
planning stages of the offenders intended terrorism-related
activities?
How socially isolated do lone-actor terrorist offenders tend to
be?
Is there a significant difference between lone offenders and
those who commit terrorism-related offenses on behalf of a
group?
Are there key life history events that may be relevant in
understanding the development of lone actors?
Are there differences between lone-actor terrorists based on
their ideology or network connectivity?
Method
Sample
The sample includes 119 individuals who engaged in or
planned to engage in lone-actor terrorism within the United
States and Europe and were convicted for their actions or died
in the commissioning of their offense. For the purposes of this
project, terrorism is defined as the use or threat of action where
1
Department of Security and Crime Science, University College London,
35 Tavistock Square, London WC1H 9EZ, U.K.
2
School of Criminology and Justice Studies, University of Massachusetts
Lowell, Health and Social Sciences Building, 1 University Avenue, MA
01854.
3
Department of Psychology, Moore Building, Pennsylvania State Univer-
sity, PA 16802.
*Presented in part at the American Society of Criminology Annual Meet-
ing in Chicago, November 2012.
Sponsored by the U.S. Department of Homeland Securitys Science and
Technology Directorate and coordinated through the U.K. Home Office.
The views and conclusions contained in this document are those of the
authors and should not be interpreted as necessarily representing the official
policies, either expressed or implied, of the Department of Homeland Secu-
rity or the Home Office.
Received 18 Oct. 2012; and in revised form 3 Jan. 2013; accepted 21
April 2013.
© 2013 American Academy of Forensic Sciences
425
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use,
distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
JForensicSci, Marc h 2014, Vol. 59, No. 2
doi: 10.1111/1556-4029.12312
Available online at: onlinelibrary.wiley.com
the use or threat is designed to influence the government or to
intimidate the public or a section of the public, and/or the use
or threat is made for the purpose of advancing a political, reli-
gious, or ideological cause. Terrorism can involve violence
against a person, damage to property, endangering a persons
life other than that of the person committing the action, creating
a serious risk to the health or safety of the public or a section
of the public, or facilitating any of the above actions. In addi-
tion to including individuals who actively planned and
conducted violent attacks, our sample includes lone actors who
engaged in nonviolent behaviors that facilitated or encouraged
violent actions carried out by others or behaviors that intended
to cause only structural damage. For example, some may priori-
tize causing infrastructural damage as in the case of isolated
dyad Ellis Edward Hurst and Joseph Martin Bailie. Both men
held grudges against tax authorities and planned to blow up a
United States Internal Revenue Service building in December
1995. They decided to plan the detonation for a Sunday even-
ing to ensure the building would be empty. Despite the 100lb
IED failing to detonate due to a faulty fuse, the timing and
delivery of the IED itself shows rational strategic thought on
behalf of the perpetrators, who sought not to cause human
injury but rather engage in an expressive act against a symbolic
target. Other examples include Ryan Gibson Anderson and
Kevin Gardner, who separately aimed to provide insider knowl-
edge of U.S. and U.K. military capabilities and Army Camp
weaknesses to wider terrorist networks.
The sample includes individual terrorists (with and without
command and control links) and isolated dyads in our actor data-
base. Individual terrorists operate autonomously and indepen-
dently of a group (in terms of training, preparation, and target
selection, etc.). In some cases, the individual may have radical-
ized toward violence within a wider group but left and engaged
in illicit behaviors outside of a formal command and control
structure. Individual terrorists with command and control links
on the other hand are trained and equipped by a groupwhich
may also choose their targetsbut attempt to carry out their
attacks autonomously. Isolated dyads include pairs of individuals
who operate independently of a group. They may become radi-
calized to violence on their own (or one may have radicalized
the other), and they conceive, develop, and carry out activities
without direct input from a wider network. Although not techni-
cally lone actors, they are included for a number of reasons.
First, a key component of this project focuses upon the network
qualities of terrorists who are not members of terrorist groups.
Second, an initial review of our cases showed that isolated dyads
often formed when one individual recruited the other specifically
for the terrorist attack. The formation of a dyad, in some cases,
may be a function of the type of terrorist attack planned. Finally,
by including these cases, it added to our sample, making the
types of inferential statistics used later more applicable.
Prior to data collection, the authors examined the academic lit-
erature on lone-actor terrorism and built an actor dictionary, pro-
ducing a list of names that fit the above criteria. Further names
were also sourced through tailored search strings developed and
applied to the LexisNexis All English News option. More
individuals were also identified through the Global Terrorism
Database developed by the National Consortium for the Study of
Terrorism and Responses to Terrorism (START) and lists of
those convicted of terrorism-related offenses in the United King-
dom and the United States. The decision was then made to limit
the population to post-1990 events because a large component of
our data would be coded from the LexisNexis archive which is
generally quite sparse before the 1990s. In total, 119 lone-actor
terrorist offenders fit the specified geographical, temporal, and
operational criteria.
Data Collection and Analysis
The codebook used in this project was developed based on a
review of literature on individuals who commit a wide range of
violent and nonviolent crimes, are victimized, and/or engage in
high-risk behaviors as well as a review of other existing
codebooks used in the construction of terrorism-related databas-
es. The variables included in the codebook spanned sociodemo-
graphic information (age, gender, occupation, family
characteristics, relationship status, occupation, employment, etc.),
antecedent event behaviors (aspects of the individuals behaviors
toward others and within their day-to-day routines), event-spe-
cific behaviors (attack methods, who was targeted), and post-
event behaviors and experiences (claims of responsibility, arrest/
conviction details, etc.).
The authors collected data on demographic and background
characteristics and antecedent event behaviors by examining and
coding information contained in open-source news reports,
sworn affidavits, and when possible, openly available firsthand
accounts. The vast majority of our sources came from tailored
LexisNexis searches. The authors also analyzed relevant docu-
ments across online public record depositories such as docu-
mentcloud.org, biographies of five lone actors in our sample
(Ted Kaczynski, Timothy McVeigh, David Copeland, Eric
Rudolph and Bruce Ivins) and all available scholarly articles.
Each observation was coded by three independent coders.
After an observation was coded, the results were reconciled in
two stages (coder A with coder B, and then coders AB with C).
In cases when three coders could not agree on particular vari-
ables, the projects postdoctoral research fellow resolved differ-
ences based on an examination of the original sources that the
coders relied upon to make their assessments. Such decisions
factored in the comparative reliability and quality of the sources
(e.g., reports that cover trial proceedings vs. reports issued in the
immediate aftermath of the event) and the sources cited in the
report. Due to time constraints, no efforts were made to check
the veracity of reporting against primary sources unless they
were readily available online.
It is important to emphasize some limitations inherent in the
sources used in this study. First, the sample only includes infor-
mation on individuals who planned or conducted incidents
reported in the media. It is possible incidents were missed that
either (i) led to convictions but did not register any national
media interest but may have been reported in local level sources
not covered in the LexisNexis archives or (ii) were intercepted or
disrupted by security forces without a conviction being made.
Second, as the level of detail reported varied significantly across
incidents, data collection was limited to what could reasonably be
collected for each case. For example, Pennsylvania state police
seized raw explosives and homemade IEDs in a 34-year-old
mans home in Milesburg, PA in December 2011. This received
no national coverage. Finally, it is often difficult to distinguish
between missing data and variables that should be coded as a
no. Given the nature of newspaper reporting, it is unrealistic to
expect each biographically oriented story to contain lengthy
passages that list each variable or behavior the offender did not
conduct (e.g., the offender was not a substance abuser, a former
convict, recently exposed to new media, etc.). For the descrip-
tive analysis that follows, where possible, the authors report or
426
JOURNAL OF FORENSIC SCIENCES
distinguish between missing data and no answers, but it should
be kept in mind that the likely result is that no answers are sub-
stantially undercounted in the analysis. In the comparisons among
lone actors based on their ideologies or network connectivity,
each variable is treated in the analysis dichotomously (e.g., the
response is either a yes, or not enough information to suggest a
yes). Unless otherwise stated, each of the below reported figures
are of the whole sample (119 individuals).
Despite these limitations, open-source accounts can provide
rich data. This has been demonstrated in other studies focusing
upon the sociodemographic characteristics, operational behaviors
and developmental pathways of members of formal terrorist
organizations. While this study has a wider remit and includes
nonincident-related behaviors, given the particularly low base
rate of lone-actor terrorism, the volume of reporting tends to be
much higher compared to campaigns of violence where trials
and convictions are a weekly occurrence. For example, educa-
tional data are accountable for 65% of our lone-actor sample.
This is compared to <10% of Gill and Horgans (8) sample of
Provisional Irish Republican Army (PIRA) militants, for whom
level of education could generally only be inferred from the indi-
viduals occupational status.
Results
Overall Characteristics and Behaviors
GenderOur lone-actor terrorist sample is heavily male-ori-
ented. In total, 96.6% are male and there are only four instances
of females engaging in such behaviors. The figure of 3.4% being
female closely resembles studies that focus upon membership
profiles of terrorist organizations/networks. For example, women
accounted for 4.9% of a sample of 1240 members of the PIRA
(9), 2.7% of a sample of 222 dissident Irish Republicans (8),
and 6.4% of Reinares (10) sample of ETA members from 1970
to 1995. There is an ongoing debate about the nature of female
recruitment and the roles women typically engage in within ter-
rorist groups (11). Much of this debate concerns the relative
degree to which women typically conduct behaviors that are
supportive of and facilitate violence as opposed to actually
committing front line violent activities. In terms of our female
subset, there is also such a distinction. Two of the females in
our sample committed violent acts. Roshonara Choudhry stabbed
a Labour Party MP, Stephen Timms, in May 2010 in revenge
for supporting the Iraq War and the subsequent deaths of inno-
cent people within Iraq. Rachelle Shelley Shannon shot Dr.
George Tiller (who was later assassinated by lone actor Scott
Roeder) outside his abortion clinic in Kansas in 1993. Shannon
was also found guilty on 30 counts of being connected to several
arson attacks against a total of nine abortion clinics. The other
two females engaged in facilitative behaviors. For example,
Shella Roma was convicted in March 2009 of disseminating ter-
rorist publications. She produced two versions of a leaflet enti-
tled, The Call, which encouraged individuals to commit terrorist
acts against Western forces. The intention was to distribute these
leaflets both from her home and outside of particular mosques
near her home in Oldham, England. Houria Chahed Chentouf
was also convicted in 2009 in the United Kingdom for possess-
ing documents likely to be useful for potential terrorists. She
was stopped at Liverpools John Lennon airport with USB stick
containing more than 7000 files including instructions on how to
set up training camps and manufacture IEDs as well as a list
of potentially suitable targets. Investigators also later found
hand-written documents that suggested Chentouf was consider-
ing moving from facilitative to violent actions. The documents
apparently considered whether she and her children should
become suicide bombers (12).
Age of First Terrorist ActivityFigure 1 below examines the
age at which offenders committed their first terrorism-related
activity that led to a subsequent arrest and conviction unless the
offender died in the course of the terrorist event itself. Offen-
ders age ranged from 15 to 69, with a mean of 33, a mode of
22, and a standard deviation of 12. This average age is much
older than studies that have focused upon Colombian militants
average age of 20 (13), the PIRAaverage age of 25 (14), and
finally al-Qaeda-related terroristsaverage age of 26 (15). In
fact, it is the second oldest sample of terrorists that the authors
are aware of, behind a sample of contemporary dissident Irish
republicansaverage age of 35 (8). Many in the dissident sam-
ple had previously been members of PIRA, however, suggesting
that their average age of first terrorist involvement would be
younger.
Figure 1 compares the lone-actor data set with data on PIRA
and the Basque separatist group Euskadi Ta Askatasuna (ETA)
in terms of the relative distribution of age groups. These groups
were chosen because they are the sole studies with comparable
and available data. The percentage of those over 30 years of age
in our sample of lone actors is substantially larger than in the
two other samples for which comparative figures are available. It
is almost two and a half times larger than in the PIRA sample
and more than eight times larger than in the ETA sample. The
proportion of those under the age of 20 is also approximately
four times smaller than in the ETA and PIRA samples. As
depicted in Fig. 1, those between 21 and 23 years of age and
those over 30 encompass more than 70% of the lone actors in
the sample, suggesting that the onset of lone-actor engagement
in terrorism has a different temporal trajectory than that of
engaging in terrorism within formal groups.
Relationship Status and Family CharacteristicsOf the 106
individuals for whom relationship status data were available,
50% were single individuals who had never married. A few
(6.6%) were in relationships but had not yet married. Almost a
quarter (24.5%) were married, and a further 18.9% had either
separated from their spouse (3.8%) or were divorced (15.1%).
The percentage of married individuals in this sample is lower
than that associated with al-Qaeda-related terrorists (73%) (14),
PIRA (41.6%) (13), and contemporary dissident republicans
0% 20% 40% 60% 80% 100%
Lone Actors
PIRA
ETA
<18
18-20
21-23
24-26
27-29
30+
FIG. 1–– Age when committing first terrorism-related offense that resulted
in conviction.
GILL ET AL.
.
LONE ACTOR MOTIVATION AND BEHAVIOR 427
(50%) (8), but higher than that associated with ETA (11.6%)
(10) and Pakistani militants (14%) (16). Given the relatively
older age of this sample, the marriage rates are low. When we
consider the oft-cited finding that criminal offending decreases
as individuals age due to biographical constraints such as mar-
riage, it is also not surprising to find such a comparatively older
sample to have a high proportion of unattached individuals.
Just more than a quarter (27.7%) had children, 34.5% were
reported not to have children, and in 37.8% of cases, data on
children were unreported. This figure is comparatively much
lower than Gill and Horgans (14) study of PIRA militants in
which 41.4% had children, especially when we take into consid-
eration that the lone-actor sample is a much older cohort of indi-
viduals.
Of the 65 observations on which parental relationship status
was available, 47.7% were married, while the remainder were
divorced (30.8%), separated (7.7%), widowed (7.7%), or never
married (3.1%).
EducationThis section outlines the distribution of educa-
tional achievement among members of the sample for which
data were available (77 individuals). In total, approximately a
quarters (24.7%) highest educational achievement was either
attending or completing high school or secondary education.
A further 32.5% either attended a community college, trade
school, or university undergraduate education without graduat-
ing. An additional 22.1% completed some form of community
college, trade school, or university education and graduated.
Another 20.8% participated in graduate school and either failed
to graduate (6.5%), graduated with a masters degree (6.5%), or
graduated with a doctoral degree (7.8%). In sum, there is a gen-
erally even distribution across the spectrum of educational
achievement (depicted in Fig. 2).
EmploymentDespite the generally high educational achieve-
ment among our cohort, this was not immediately apparent when
viewing the types of employment they were in at the time of
their terrorism-related activity. Employment data were available
for 112 of the sample. Of these individuals, 40.2% were unem-
ployed and a further 9.8% were still students. The other half of
the sample were employed but mainly concentrated within the
service industry (23.2%). Much smaller percentages were in pro-
fessional occupations (10.7%), construction (4.5%), clerical/
administrative/sales positions (4.5%), and agriculture (1.8%).
These figures are largely different from the studies cited earlier
on PIRA and ETA as well as Horgan and Morrisons (17)
study of dissident republicans particularly in terms of those
unemployed and those in the construction industry (see Fig. 3).
In both the PIRA and ETA samples, the construction industry
was the largest employer. PIRA and ETA were comprised of
comparatively fewer unemployed individuals compared to the
lone-actor terrorist data set.
Military ExperienceA quarter (26%) had military experi-
ence. Of this subset, 76.7% had since left the army, the vast
majority of whom for normal reasons. Some, however, had been
ejected from the army for various offenses (such as racist behav-
ior in the case of Sean Gillespie), and others had been suspended
and faced court-martial (such as Naser Jason Abdo on child por-
nography charges). Of those who had military experience, 23.3%
had actual combat experience.
Criminal and Other Illicit ActivitiesSignificantly, 41.2% of
the sample had previous criminal convictions, and this figure is
far higher than what is anecdotally suggested regarding members
of formal terrorist organizations, who prefer recruits with clean
records as they are unlikely to raise red flags among the security
community. Offenses included threats to life, first-degree rob-
bery, criminal damage, custodial and second-degree assault, fire-
arms offenses including possession, obstructing law enforcement
officers, drunk driving, grand larceny, vehicle theft, blackmail,
lewd and disorderly conduct, drug possession, counterfeiting,
criminal use of explosives, vandalism, attempted murder, child
neglect, restraining order violations, theft, income tax issues,
child pornography possession, graffiti, and somewhat strangely
possession of a carcass of a protected barn owl. Of this subset,
63.3% served time in jail. During jail time, at least 32.3% of this
subset adopted the ideology and radicalized (as reported in
open-source news articles) for the event they later conducted or
planned. Of the full sample, 37.8% had previously engaged in
violent behaviors. More than a fifth (22.7%) had a history of
substance abuse. At least 27.3% had no previous convictions or
history of imprisonment.
Mental HealthJust less than a third (31.9%) had a history of
mental illness or personality disorder. In the vast majority of
these cases, the diagnosis had been made before the individual
engaged in terrorism-related activities. Naveed Afzal Haq, for
example, had been diagnosed with bipolar disorder. Of this
cohort, many were prescribed medicine, others were committed
into residential programs and psychiatric institutions, others were
hospitalized, and some engaged with counseling services. Some
lone actors were only diagnosed upon their arrest and subsequent
trial (for example, Ted Kaczynski was diagnosed with paranoid
schizophrenia).
High School
25%
Some University
32%
Undergraduate
Degree
22%
Graduate School
(Dropped Out)
7%
Master's Degree
6%
PhD
8%
FIG. 2–– Highest educational achievement.
0% 20% 40% 60% 80% 100%
ETA
Dissidents
PIRA
Lone Actors
Unemployed
Services/Agriculture
Student
ConstrucƟon
Clerical/Sales/Admin
Professional
Other
FIG. 3–– Comparative occupational category breakdown.
428 JOURNAL OF FORENSIC SCIENCES
Ideological Justifications
As Fig. 4 illustrates, the lone-actor terrorists in our sample
had a range of ideologies. Religiously inspired lone actors con-
stitute the largest set of actors at 43%. This is perhaps not a sur-
prising finding given how loosely connected al-Qaedas
transnational network has become over time and al-Qaedas
growing emphasis upon lone-actor attacks (for example, al-Qae-
da in the Arabian Peninsulas Inspire magazine has been a con-
sistent advocate of this strategy). Those inspired by right-wing
ideologies constitute the second largest group representing a
third of the total sample. The third largest grouping is a cluster-
ing of individuals driven by single-issue causes such as antiabor-
tion or environmental campaigning. The balance between these
groups has changed over time. Only 7.8% of religiously oriented
lone actors engaged in their terrorist actions before 2001,
whereas the corresponding figures for right-wing extremists is
32.5% and single-issue offenders is 47.6%.
Historically, there have been very few lone-actor incidents
involving left-wing or nationalist inspired individuals. For four
of our cohort, it was extremely difficult to categorize the individ-
uals ideological orientation and motivation. This is either
because the individuals ideology was self-made (as in the case
of Ted Kaczynski) or economically oriented (as in the case of
Dwight Watson and arguably Bruce Ivins).
Awareness of Intentions
In most cases, other individuals knew something concerning
some aspect of the offenders grievance, intent, beliefs, or
extremist ideology prior to the event or planned event. In 58.8%
of cases, the offender produced letters or public statements prior
to the event outlining his/her beliefs (but not necessarily his/her
violent intent). This figure aggregates both virtual and printed
statements in newspapers and leaflets, etc. In 82.4% of the cases,
other people were aware of the individuals grievance that
spurred the terrorist plot, and in 79%, other individuals were
aware of the individuals commitment to a specific extremist ide-
ology. In 63.9% of the cases, family and friends were aware of
the individuals intent to engage in terrorism-related activities
because the offender verbally told them. This is comparatively
lower figure than the 81% found in a study of school shooters
(18). In 65.5% of cases, the offenders expressed a desire to hurt
others. This desire was communicated through either verbal or
written statements. These findings suggest therefore that friends
and family can play important roles in efforts that seek to
prevent terrorist plots. Of those who were married or in a
relationship, 24.2% of the offenders spouses or partners were
members of a wider network associated with the ideology that
inspired the lone-actor terrorist. Finally, in 22.7% of the cases,
the individual provided a specific preterrorist event warning.
There is also much evidence to suggest that others were aware
of the individuals disposition, but not necessarily their intent. In
53.8% of the cases, the offender was characterized by close
friends/family as an angry individual. Of this subsample (64
individuals), there is a suggestion that the offenders anger was
noticeably increasing in 62.5% of the cases.
Pre-Event Behaviors
This section provides an overview of our findings concerned
with the behaviors the individual engaged in prior to the terrorist
event or planned event. A fifth (20.2%) of the total sample con-
verted to a religion before engaging or planning to engage in an
event. Not all of those who converted were necessarily reli-
giously motivated offenders, however. Some, such as Leo Fel-
ton, were motivated by right-wing ideologies. Others, such as
James Kopp, were single-issue offenders. Of the al-Qaeda-
inspired offenders, religious converts account for 37.3%. The
religiosity of 29.4% of the al-Qaeda-inspired lone-actor terrorists
noticeably increased in the buildup to their terrorist event or
planned event.
Half (50.4%) changed address within the 5 years prior to their
terrorist event planning or execution. Significantly, of those who
did change address, 45% did so within 6 months of their even-
tual terrorist attack or arrest. A further 20% changed address
between seven and twelve months prior to the terrorist event or
preemptive arrest. Altogether, this means that just less than a
third of our total sample (32.8%) changed address in the year
before their terrorist plot either occurred or was prevented.
As noted earlier, 40.2% were unemployed at the time of their
arrest or terrorist event. Many were chronically unemployed and
consistently struggled to hold any form of employment for a sig-
nificant amount of time. Of the unemployed subset, however,
approximately a quarter (26.6%) had lost their jobs within
6 months and a further 15.5% between seven and twelve months
before the event. On a related note, 25.2% experienced financial
problems. Of this subsample (30 individuals), 56.6% experienced
financial problems within a year of their terrorist attack or plot.
Many (32.8%) of the offenders were characterized as being
under an elevated level of stress due to a number of reasons. Of
this subsample, 74.3% of the cases of elevated stress occurred
within a year of the terrorist attack or plot. Very few had
recently (e.g., within 5 years) experienced a death in their family
(6.7%) that may have served as a catalyst for the intended vio-
lence that followed. Very few dropped out of school or left uni-
versity (10.1%) before their terrorist event or planned event.
Approximately one in five of those lone actors in gainful
employment demonstrated worsening work performance in the
buildup to their terrorist event or plot. Very few (6.7%) were
interrupted in working on a proximate goal in the year before
their terrorist event or planned event. Some (12.6%) noticeably
increased their physical activities and outdoor excursions in the
buildup to their terrorist event. At least 15.1% subjectively expe-
rienced being the target of an act of prejudice or unfairness. On
a related note, 19.3% subjectively experienced being disrespect-
ed by others, while 14.3% experienced being the victim of
verbal or physical assault. At least 25.2% of the full sample was
characterized as suffering from long-term sources of stress.
Al-Qaeda
Inspired 43%
Right-Wing 34%
Single Issue 18%
Other 5%
FIG. 4–– Lone-actor ideological orientation.
GILL ET AL.
.
LONE ACTOR MOTIVATION AND BEHAVIOR 429
Social IsolationMore than a quarter (26.9%) adopted their
radical ideology when living away from home in another town,
city or country. At least 37% lived alone at the time of their
event planning and/or execution, a further 26.1% lived with oth-
ers, and no data were available for the remaining cases. This is
perhaps a surprisingly low figure considering that the vast major-
ity of plots and preparations were carried out within the lone
offenders home. More than half (52.9%) were characterized as
socially isolated by sources within the coded open-source
accounts.
On occasion, lone-actor terrorists experienced problems with
personal relationships. In these cases, social isolation was not a
long-standing occurrence but instead was derived from more
recent interpersonal conflict. For example, 31.1% experienced
problems in close personal relationships (e.g., family, romantic
relationships). Of this subsample (37 individuals), 32.4% experi-
enced these difficulties within the 6 months prior to their terror-
ist attacks or plots. At least 10.9% of the full sample
experienced being ignored or treated poorly by someone impor-
tant to them in the buildup to their terrorist event or planned
event. Additionally, 8.4% experienced someone important
demonstrating that they did not care about the individual in the
buildup to their offense.
Behaviors Within a Wider Network One in six (16.8%)
sought legitimization from religious, political, social, or civic
leaders prior to the event they planned. Perhaps the most famous
case of this behavior is the case of Nidal Malik Hassan, who
sent Anwar al-Awlaki at least 18 emails between December
2008 and June 2009 asking various questions concerning the
legitimacy of killing innocents and when engaging in jihad is
appropriate. A similar figure (14.3%) had previously engaged in
fundraising or financial donations to a wider network of individ-
uals associated with either licit pressure groups or illicit groups
who espoused violent intentions.
Importantly, 33.6% of the sample had recently joined a wider
group, organization, or movement that engaged in contentious
politics. Many of these groups engaged in legal activities but
shared similar ideologies to those the lone actor used to justify
planning or conducting his/her terrorist activity. A similar num-
ber (31.9%) had also become recently exposed to new social
movement or terrorism-related media.
Links to a Wider NetworkApproximately a third of the
sample (36.1%) had family members or close associates known
to have been involved in political violence or criminality. Just
less than half (47.9%) interacted face-to-face with members of a
wider network of political activists, and 35.3% did so virtually.
In 68.1% of the cases, there is evidence to suggest that the indi-
vidual read or consumed literature or propaganda from a wider
movement. There is evidence to suggest in 20 of the cases
(16.8%) that there may have been wider command and control
links specifically associated with the violent event that was
planned or carried out.
One in ten of the sample had been either rejected or ejected
from a wider network or group that engaged in legal contentious
politics. Perhaps the most famous example is that of Timothy
McVeigh, who had been ejected from various right-wing affili-
ated organizations such as the National Rifle Association.
In terms of the planning of the terrorist event itself, there is
also much evidence that others were aware of the offenders
specific intent of engaging in terrorism-related activities. In
approximately a third of the cases (34.5%), the lone actor had
tried to recruit others or form a group prior to the event. In
57.7% of cases, other individuals possessed specific information
about the lone actors research, planning, and/or preparation
prior to the event itself. In nearly a quarter of all cases (23.5%),
other individuals were involved in procuring weaponry or tech-
nology that was used (or planned to be used) in the terrorist
event but did not themselves plan to participate in the violent
actions. In 16 cases, other individuals helped the lone actor
assemble an explosive device.
More than half of the lone actors (52.9%) characterized their
actions as associated with a wider group or movement or
claimed to be part of a wider group or movement while a much
smaller figure (5.9%) framed their actions as driven by personal
grievances. For many, this meant characterizing their actions as
being associated with an established group such as al-Qaeda.
Others, however, claimed their attacks on behalf of a group
whose actual existence is highly questionable. For example, Ted
Kaczynskis letter to the New York Times claimed his group,
called FC, was responsible for the bombing attacks. Similarly,
no evidence has emerged within the open-source literature that
the contemporary manifestation of the Knights Templar refer-
enced by Anders Breivik actually exists.
Finally, at times, there appears to be a direct form of knowl-
edge diffusion between lone actors within our sample. Evidence
suggests that approximately a quarter (26.9%) read or consumed
literature or propaganda concerning other lone-actor terrorists.
Additionally, evidence also suggests that 15.1% consumed or
read literature or propaganda produced by other lone-actor terror-
ists.
Attack and Plot Related Behaviors
Training for the plots typically occurred through a number of
ways. Approximately a fifth of the sample (21%) received some
form of hands-on training, while 46.2% learned through virtual
sources. In approximately half the cases (50.4%), investigators
found evidence of bomb-making manuals within the offenders
home or property. The fact that much strategic and tactical plan-
ning goes into lone-actor terrorist events is demonstrated by the
finding that 29.4% of offenders engaged in dry runs of their
intended activities (also as not all of the sample intended to
engage in violence, this finding would likely be even higher if
nonviolent offenders were excluded). Of those who did make
dry runs or preparatory trips (35 individuals), 57.1% did so
within a year of the eventual attack. Very few (4.2%) used drugs
or alcohol in the commissioning of a terrorist attack.
In terms of plotting, 41.2% of the offenders specifically tar-
geted, or intended to target, people, 11.8% targeted property,
and a further 32.8% plotted against a combination of both target
types. When we break down plots by the nature of the attack
location, it is evident that the most commonly sought-after target
were civilians (27.7%), followed by government-related targets
(23.5%), businesses (17.6%), religious targets (e.g., mosques),
(8.4%) and military targets (6.7%). Compared to statistics pro-
vided by Global Terrorism Database developed by the National
Consortium for the Study of Terrorism and Responses to Terror-
ism, lone-actor terrorists appear to plan or perpetrate attacks
against military targets on a far less consistent basis compared to
terrorist groups. This may be a function of capability. Most
(58%) lone-actor terrorist plots are conceived to take place in
public locations. In 24.4% of cases, the offender has had a previ-
ous history with the location of the attack (e.g., was previously
employed there). Just less than a half (47.1%) of lone actors
430
JOURNAL OF FORENSIC SCIENCES
possessed a stockpile of weapons for the commissioning of the
offense.
Just over half of the observations (51.2%) successfully
executed their terrorist attack. Of this sample (n = 61), the
majority of offenders (61.2%) used their personal vehicle to tra-
vel to the attack location, while others took public transport
(16.1%), walked (9.6%), or rented a car (12.9%).
In 21% of the cases, the individual expressed remorse/regret
following their event and subsequent arrest. Of these cases (25
individuals), 44% later changed their beliefs/ideological orienta-
tion. At least 16.6% expressed no remorse for their actions, and
data were unavailable for the rest of the cases.
Comparing Subgroups of Lone-Actor Terrorists
The descriptive analysis of our data above illustrates that there
is no reliable profile of a lone-actor terrorist. In this section, the
authors examine specific subgroups of lone-actor terrorists to
explore whether the individual characteristics and behaviors of
lone-actor terrorists differ across these distinctions.
Comparing Lone-Actor Terrorists by Ideology
Terrorist groups are commonly distinguished across motiva-
tional and ideological domains (1921). The three most preva-
lent ideologies held by members of our lone-actor terrorist data
set were right-wing, single-issue (animal rights, antiabortion,
environmentalism), and al-Qaeda-related ideologies. In Table 1,
the major differences in individual characteristics and antecedent
event behaviors associated with lone actors who held these ide-
ologies are outlined. To identify differences between ideological
groups, 2 9 2 chi-squared analyses (or Fishers exact tests
where appropriate) were run for each ideological domain against
each antecedent and behavioral variable (e.g., right wing vs.
single issue/al-Qaeda). A one-way ANOVA comparison of
means test was used for the average age variable.
As the results suggest, there are distinctions among lone-actor
terrorists with specific types of ideologies. The average age of
al-Qaeda-related lone actors was 10 years younger than that of
either the right-wing or single-issue cohorts. Members of this
subgroup (compared to a combination of right-wing and single-
issue lone actors) were also significantly more likely to be
students or have a university degree and/or some experience of
university. They were significantly less likely to have previous
criminal convictions or experience of imprisonment at the time
of their terrorist event. Given the ideological beliefs of this sub-
group, it is also not surprising that they were significantly more
likely to seek legitimization from religious, political, social, or
civic leaders prior to their terrorist event or plot and significantly
more likely to be religious converts. They were also significantly
more likely to learn through virtual sources and to be living
away from home during the phase when they adopted their
extremist ideology. There was also a significantly higher indica-
tion of command and control links with this subgroup (mainly
through others helping them procuring weaponry or through
others knowing about the specific attack plan). Historically, al-
Qaeda-related lone-actor terrorists have been significantly less
likely to be U.S.-based compared to those espousing right-wing
or single-issue ideologies. They have also been significantly less
likely to join a wider pressure group or social movement in the
buildup to their terrorist event and significantly less likely to
successfully execute their terrorist attack.
Compared to both single-issue and al-Qaeda-inspired offend-
ers, right-wing lone-actor terrorists were significantly less likely
to have experienced any form of university education, work as a
professional, be a student, be a religious convert, or be living
away from home when they adopted their radical ideology
or have children. They were more likely to be employed in
TABLE 1–– Comparing lone actors across ideological domains.
Right Wing (n = 40) Single Issue (n = 21) Al-Qaeda Related (n = 52)
Town size <20,000 37.5%*** 28.6% 9.6%***
University experience 15%*** 52.4% 50%**
Worked in construction 12.5%*** 0% 0%**
Worked as a professional 2.5%* 14.3% 11.5%
Student at time of event 2.5%* 4.8% 17.3%**
Unemployed 50%* 38.1% 30.8%
Verbal statements to friends/family about intent or beliefs 52.5%** 71.4% 71.2%
Religious convert 2.5%*** 19% 36.5%***
Sought legitimization 7.5%** 9.5% 28.8%***
Lived away from home when ideology adopted 15%** 19% 38.5%***
Others helped procure weaponry 10%*** 33.3% 32.7%*
Engaged in dry runs 17.5%** 47.6%** 30.8%
Recently joined a wider group/movement 47.5%** 38.1% 23.1%**
Evidence of command and control links 5%** 4.8% 30.8%***
Based in the United States 52.5% 71.4%*** 28.8%***
In a relationship 20% 52.4%*** 21.2%
Previous criminal conviction 50% 61.9%** 26.9%***
Previously imprisoned 27.5% 47.6%** 19.2%*
Provided a pre-event warning 17.5% 38.1%* 21.2%
Spouse/partner part of a wider movement 5% 19%** 3.8%
Learned through virtual sources 37.5% 19%*** 65.4%***
History of mental illness 30% 52.4%** 25%
Others aware of individuals planning 52.5% 38.1%** 69.2%**
Children 15%** 42.9%* 28.8%
University degree 5% 4.8% 17.3%**
Average age 36.3 years 36.8 years 26.7 years***
Successful execution of terrorist attack 57.5% 66.7% 40.4%**
*p < 0.1; **p < 0.05; ***p < 0.01.
GILL ET AL.
.
LONE ACTOR MOTIVATION AND BEHAVIOR 431
construction at the time of their terrorist event, to be based in a
town with a population smaller than 20,000, and to have joined
a wider pressure group or social movement before their terrorist
action. In terms of specific event planning activities, they were
significantly more likely to solely obtain the weapons and tech-
nology needed for the event but also significantly less likely to
engage in dry runs, display evidence of command and control
links, make verbal statements to friends and family about their
intent or beliefs, or seek legitimization for their intended action
from epistemic authority figures.
Compared to both al-Qaeda and right-wing offenders, single-
issue lone-actor terrorists were significantly more likely to be in
a relationship (and to have a spouse involved in a wider move-
ment of activist politics), have children, be based in the United
States, have previous criminal convictions and have previously
been imprisoned. More than half had a history of mental illness.
They were also significantly more likely to engage in dry runs
and provide pre-event warnings and far less likely to learn
through virtual sources. Single-issue lone-actor terrorists were
also significantly less likely to have others aware of their
research, planning, or intent to engage in a terrorist attack.
There was very little to differentiate among these subgroups
of lone-actor terrorists in terms of making verbal statements to a
wider audience outside of their immediate friends and family or
other people knowing about the individuals grievance or
extremist ideology prior to the event. There were also no differ-
ences in their histories of substance abuse, military engagement,
and experiences of hands-on training; engagement with literature
and propaganda (of a wider movement and of other lone actors);
face-to-face interactions with members of a wider network; or
possession of close associates involved in criminal activities.
Comparing Lone-Actor Terrorists by Network Connectivity
While comparing and contrasting lone-actor terrorists across
ideological domains has revealed some interesting results,
perhaps a more important comparison for the practitioner com-
munity is one that examines lone-actor terrorists based on how
operationally connected they are to a broader network of acti-
vists. Depending upon the level of connectivity, different investi-
gative strategies or disruption efforts may be necessary. Table 2
illustrates the statistically significant differences between individ-
ual terrorists without command and control links, and individual
terrorists with command and control links and isolated dyads.
Compared to isolated dyads and those with command and
control links, the results suggest that individuals without
command and control links were more likely to have military
experience, previous criminal convictions, be based in the United
States, hold either single-issue or right-wing ideologies, be char-
acterized as socially isolated, and have a history of mental ill-
ness. They were significantly less likely to learn through virtual
sources, increase their religiosity before their event, recently join
a wider pressure group or social movement, attempt to recruit
others, or have family or close associates involved in political
violence or crime. Unsurprisingly, compared to both those with
command and control links and isolated dyads, those without
command and control links were also significantly less likely to
interact either face-to face or virtually with members of a wider
network or have others aware of their planning, help build their
IEDs, or help procure weaponry. They were also significantly
less likely to be al-Qaeda inspired. They were also significantly
more likely to successfully execute their terrorist attack.
Apart from network-related behaviors, there is little to differ-
entiate between those with command and control links with
those belonging to the other two subgroups. They were signifi-
cantly more likely to have had others notice an increase in their
religiosity and be inspired by al-Qaeda. They were significantly
less likely to be influenced by right-wing or single-issue ideolo-
gies, be characterized as socially isolated, have previous criminal
convictions, military experience, or be based in the United
States. They were also significantly less likely to successfully
execute their terrorist attack.
TABLE 2–– Comparing lone actors by network connectivity.
Individuals Without Command
and Control Links (n = 87) (%)
Individuals With Command
and Control Links (n = 21) (%)
Isolated Dyads
(n = 11) (%)
Based in the United States 55.2*** 4.8*** 36.4
Previous military experience 31*** 4.8** 9.1
Previous criminal conviction 47.1** 19** 36.4
Held a PhD 2.3 0 18.2**
Lived alone 40.2 38.1 9.1**
Lived away from home when ideology adopted 23 42.9* 27.3
Received training 20.7 33.3 0*
Learnt through virtual sources 40.2*** 66.7* 72.7*
History of mental illness 35.6** 19 9.1
Socially isolated 57.5* 33.3* 45.5
Recently joined a wider group/movement 27.6** 47.6 45.5
Noticeable increase in religiosity 23*** 61.9*** 27.3
Family/close associates involved in political violence/crime 27.6*** 57.1** 63.6**
Interacted face-to-face with wider network 39.1*** 61.9 90.3***
Interacted virtually with wider network 28.7*** 57.1** 63.6*
Others helped procure weaponry 17.2*** 38.1* 45.5*
Others helped build IED 6.9*** 33.3*** 27.3
Others aware of individuals planning 42.5*** 100*** 100***
Attempted to recruit others 27.6** 33.3 81.8***
Consumed propaganda from a wider movement 65.5* 85.7* 72.7
Al-Qaeda related 33.3*** 76.2*** 63.6
Single issue 23** 4.8* 0
Right wing 39.1** 9.5** 36.4
Successfully executed an attack 57.5** 33.3* 27.3
*p < 0.1; **p < 0.05; ***p < 0.01.
432 JOURNAL OF FORENSIC SCIENCES
For isolated dyads, it is also largely the case that little sepa-
rates them from the other two subgroups other than network-
related behaviors. Compared to the other two subgroups, isolated
dyads were significantly more likely to attempt to recruit others
and hold a PhD. Isolated dyads were significantly less likely to
receive hands-on training or live alone.
Comparing Successful and Foiled Lone-Actor Terrorists
This section outlines the significant differences between those
lone-actor terrorists who successfully executed an attack and
those who did not. To calculate whether differences were signifi-
cant, chi-squared tests were used for each variable (Table 3).
Interestingly, those who successfully committed an attack
were significantly less likely to engage in a number of network-
related behaviors including having others aware of their attack
planning, attempting to recruit others, learning through virtual
sources, possessing bomb-making manuals, being recently
exposed to new media, interacting virtually with members of a
wider network, and consuming/reading propaganda related to
either a wider group or other lone-actor terrorists. Successful
lone-actor terrorists, however, were significantly more likely to
have university experience, be characterized as being socially
isolated, have a history of mental illness, or have previously
been rejected from a wider group or movement.
Discussion and Conclusion
This article focused on 119 lone-actor terrorists and the behav-
iors that underpinned the development and/or execution their
plots. In total, seven key findings were identified. This section
summarizes these findings and highlights their implications from
a preventative and investigative perspective before concluding
with a discussion of potential avenues for future research.
Findings and Implications
Finding 1: There was no uniform profile of lone-actor terror-
ists.
Although heavily male-oriented, there were no uniform
variables that characterized all or even a majority of lone-actor
terrorists. The sample ranged in age from 15 to 69. Half were
single, 24% were married, and 22% were separated or divorced.
Twenty-seven percent had children. Educational achievement
varied substantially with approximately a quarter either having
attended or finishing high school, approximately a third of the
sample having attended, but not graduating from some form of
university, 22% completing an undergraduate degree, and 21%
having attended or finishing some form of graduate school. In
total, 8% held a PhD, while 40% of the sample was unemployed
at the time of their terrorist attacks or arrests, 50% held jobs
(11% professional positions), and 10% were students. Twenty-
six percent had served in the military. Finally, forty-one percent
had previous criminal convictions, 31% had a history of mental
health problems, and 22% had a history of substance abuse.
Thus, no clear profile emerged from the data. Even if such a
profile were evident, however, an over-reliance on the use of
such a profile would be unwarranted because many more people
who do not engage in lone-actor terrorism would share these
characteristics, while others might not but would still engage in
lone-actor terrorism.
Finding 2: In the time leading up to most lone-actor terrorist
events, evidence suggests that other people generally knew about
the offenders grievance, extremist ideology, views and/or intent
to engage in violence.
For a large majority (83%) of offenders, others were aware of
the grievances that later spurred their terrorist plots or actions. In
a similar number of cases (79%), others were aware of the indi-
viduals commitment to a specific extremist ideology. In 64% of
cases, family and friends were aware of the individuals intent to
engage in a terrorism-related activity because the offender ver-
bally told them. In 58% of cases, other individuals possessed
specific information about the lone actors research, planning,
and/or preparation prior to the event itself. Finally, in a majority
(59%) of cases, the offender produced letters or made public
statements prior to the event to outline his/her beliefs (but not
his/her violent intentions). These statements include both letters
sent to newspapers, self-printed/disseminated leaflets, and state-
ments in virtual forums.
These findings suggest that friends, family, and coworkers can
play important roles in efforts that seek to prevent or disrupt
lone-actor terrorist plots. In many cases, those aware of the indi-
viduals intent to engage in violence did not report this informa-
tion to the relevant authorities. It is important therefore to
provide information to the wider public on the behavioral indica-
tors of radicalization to violence as well as appropriate outlets
for this information to be reported and subsequently investigated.
In any event, this finding may have significant implications for
the development of operational investigations.
Indeed, most of the variables related to others having knowl-
edge of the lone actors views and intent were far more common
across lone actors than any sociodemographic characteristics.
This suggests that lone-actor terrorists should largely be charac-
terized by what they do rather than who they are.
Finding 3: A wide range of activities and experiences
preceded lone actors plots or events.
Although the authors found it is more important to focus on
what lone-actor terrorists do than who they are, it is still impor-
tant to recognize that no single set of behaviors underpins lone-
actor terrorism. Half of the sample changed address at least five
years prior to their terrorist event planning or execution. Of the
40% who were unemployed, 27% had lost their jobs within six
months, and a further 16% between seven and twelve months
before the event. On a related note, 25% experienced financial
problems. Thirty-three percent of the offenders were characterized
TABLE 3–– Comparing successful lone actors to intercepted lone actors.
Did the Individual Successfully
Commit an Attack?
Yes (n = 61)
(%)
No (n = 58)
(%)
University experience 54.1*** 24.1
Socially isolated 70.5*** 34.5
History of mental illness 39.3* 24.1
Previously rejected from wider group 16.4** 3.4
Others aware of research/planning
or preparation for event
36.1 79.3***
Attempted to recruit others 24.6 44.8**
Learnt through virtual sources 29.5 63.8***
Bomb-making Manuals in home 31.1 70.7***
Recently exposed to new media 19.7 41.4***
Interacted virtually with wider network 24.6 46.6**
Read or consumed literature/propaganda
from a wider movement
52.5 84.5***
Read or consumed literature/propaganda
about other lone actors
11.5 43.1***
Read or consumed literature/propaganda
of other lone Actors
8.2 22.4**
*p < 0.1; **p < 0.05; ***p < 0.01.
GILL ET AL.
.
LONE ACTOR MOTIVATION AND BEHAVIOR 433
as being under an elevated level of stress due to a number of rea-
sons. Of this subsample, 74% experienced elevated stress within
a year of the terrorist plot or event. Approximately one in five of
those lone actors in gainful employment demonstrated worsening
work performance in the buildup to their terrorist plot or event.
Fifteen percent subjectively experienced being the target of an act
of prejudice or unfairness, 19% subjectively experienced being
disrespected by others, and 14% experienced being the victim of
verbal or physical assault. A fifth of the sample converted to a
religion before engaging or planning to engage in an event. Thir-
teen percent noticeably increased their physical activities and out-
door excursions.
Thus, behaviorally, the lone-actor terrorist sample was also
diverse. The behaviors related to the individuals radicalization
and trajectory into terrorism were not overly similar from case to
case. Similarly, the rhythm and tempo of each developmental
trajectory also differed.
Finding 4: Many but not all lone-actor terrorists were socially
isolated.
More than a quarter of the sample (27%) adopted their radical
ideology when living away from home in another town, city, or
country. Thirty-seven percent lived alone at the time of their
event planning and/or execution, and 53% were characterized as
socially isolated by sources within the coded open-source
accounts.
Some lone-actor terrorists experienced problems with personal
relationships. In these cases, social isolation tended not to be a
long-standing occurrence but instead was derived from more
recent interpersonal conflict. For example, 31% experienced
problems in close personal relationships (e.g., family, romantic
relationships). Of this subsample, 33% experienced these diffi-
culties within the 6 months prior to planning or conducting
their terrorist event. Eleven percent of the full sample experi-
enced being ignored or treated poorly by someone important to
them in the buildup to their terrorist plot or event. Additionally,
8% experienced someone important to them demonstrating that
they did not care about the individual in the buildup to their
offense.
A popular perception exists that lone-actor terrorists are
isolated from the rest of society while their grievances grow and
plots develop. This is perhaps best illustrated by the example of
Ted Kaczynski, the so-called Unabomber. Collectively, how-
ever, lone-actor terrorists are more likely to be socially embed-
ded within wider networks than be socially isolated. While those
who are socially isolated are a minority, they do represent a spe-
cific threat to investigations that rely upon intercepting commu-
nications or receiving warnings from friends and family. Efforts
aimed at combating socially isolated lone actors may addition-
ally need to consider issues pertaining to the supply chain of
weapons, bombing materials, and the operational manuals that
are available online.
Finding 5: Lone-actor terrorists regularly engaged in a detect-
able and observable range of activities with a wider pressure
group, social movement, or terrorist organization.
Approximately a third of the sample had recently joined a
wider group, organization, or movement that engaged in conten-
tious politics. Just less than a half (48%) interacted face-to-face
with members of a wider network of political activists, and 35%
did so virtually. In 68% of the cases, there is evidence to suggest
that the individual read or consumed literature or propaganda
associated with a wider movement. Fourteen percent previously
engaged in fundraising or financial donations to a wider network
of individuals associated with either licit pressure groups or
illicit groups who espoused violent intentions. One in six (17%)
sought legitimization from religious, political, social, or civic
leaders prior to the event they planned.
There is evidence to suggest that in 17% of the cases there
may have been wider command and control links specifically
associated with the violent event that was planned or carried out.
In approximately a third of the cases (35%), the lone actor had
tried to recruit others or form a group prior to the event. In 24%
of cases, other individuals were involved in procuring weaponry
or technology that was used (or planned to be used) in the
terrorist event but did not themselves plan to participate in
the violent actions. In 13% of cases, other individuals helped the
lone actor assemble an explosive device.
Much of the concern regarding lone-actor terrorism stems
from the particular challenges of detecting and intercepting lone-
actor terrorist events before they occur. Although they vary sig-
nificantly in their effectiveness, there is a common perception
that lone-actor plots are virtually undetectable. The traditional
image of a lone-actor terrorist is that of an individual who cre-
ates his/her own ideology and plans and executes attacks with
no help from others. Our findings suggest, however, that many
lone-actor terrorists regularly interact with wider pressure groups
and movements either face-to-face or virtually. This suggests
that traditional counterterrorism measures (such as counterintelli-
gence, HUMINT, interception of communications, surveillance
of persons etc.) may have applicability to the early detection of
certain lone-actor terrorists at specific moments in their pathway
toward violence.
Finding 6: Lone-actor terrorist events were rarely sudden and
impulsive.
Training for the plot typically occurred in a number of ways.
Approximately a fifth of the sample (21%) received some form
of hands-on training, while 46% learned through virtual sources.
In half the cases, investigators found evidence of bomb-making
manuals within the offenders home or on his or her property.
The fact that much strategic and tactical planning goes into lone-
actor terrorist events is demonstrated by the finding that 29% of
offenders engaged in dry runs of their intended activities.
Typically, lone-actor terrorist events emerge from a gradual
chain of behaviors. This chain includes the steps of adopting an
extremist ideology, thinking about engaging in violence, acquir-
ing the necessary materials and/or training, and finally commit-
ting the offense. These behaviors may be observable prior to the
commission of events. Although the development of a lone-actor
terrorist event is rarely impulsive, at times there is very little
time between the offender choosing to use violence and commit-
ting an attack.
Finding 7: Despite the diversity of lone-actor terrorists, there
were distinguishable differences between subgroups.
While no uniform profile exists across our sample, there were
significant differences when we compared subgroups. For exam-
ple, compared to right-wing offenders and single-issue offenders,
those inspired by al-Qaeda were younger and more likely to be
students and to have sought legitimization from epistemic
authority figures. They were also more likely to learn through
virtual sources and display some form of command and control
links. Right-wing offenders were more likely to be unemployed
and less likely to have any university experience, make verbal
statements to friends and family about their intent or beliefs, and
engage in dry runs or obtain help in procuring weaponry. Sin-
gle-issue offenders were more likely to be in a relationship, have
criminal convictions, have a history of mental illness, provide
specific pre-event warnings, and engage in dry runs. They were
434
JOURNAL OF FORENSIC SCIENCES
less likely to learn through virtual sources or have others aware
of their planning.
This suggests the importance of not treating all lone-actor
terrorists homogeneously and may have implications both for
prevention and disruption as well as subsequent investigation.
Future Directions
While the data, analysis, and findings throughout this article
are novel and important, it has only scratched the surface of
what is a deeply complex and unfolding contemporary phenome-
non. Together the results suggest the importance of focusing
upon an analysis of behavior rather than attempting to identify
and subsequently interpret what are realistically only semi-stable
(at best) sociodemographic characteristics. What we lack, how-
ever, is an adequate control group to fully realize the signifi-
cance of some of the descriptive findings. While the subgroup
comparisons consistently found significant differences, it would
be worthwhile to open the observations and data collection pro-
tocols to those individuals involved in fully or semi-autonomous
groups. Through such an endeavor, a comparative approach
would illustrate whether the descriptive findings related to ante-
cedent behaviors and experiences are inherent to lone-actor ter-
rorists or whether they are part of a wider trajectory in terrorism
as a whole. An understanding of these dynamics would provide
a wider evidence base to inform counterterrorism policies and
practices. On a much more aspirational scale, there is also little
evidence of the prevalence of these variables among the wider
public and thus how much they truly distinguish lone-actor
terrorists from law-abiding citizens.
Other methodologies will also provide other further insight.
At the time of writing, there remain no publicly available inter-
views undertaken by researchers with lone-actor terrorists with
the specific purpose of understanding how individuals decide to
undertake violence as an individual, absent of formal terrorist
group membership. Little is also known about the individual
sociopsychological and practical constraints that need to be over-
come to successfully execute a lone-actor terrorist attack.
Finally, the finding that many of our sample had performed acts
of criminality prior to their terrorist plotting suggests that it may
be worthy to analyze these individuals from a criminal careers
perspective. Such a perspective would provide insight into how
individuals desist from one illegal activity and ultimately transi-
tion toward other illegal (but politically or socially driven) activ-
ities.
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Additional information and reprint requests:
Paul Gill, Ph.D.
Department of Security and Crime Science
University College London
35 Tavistock Square
London WC1H 9EZ
U.K.
E-mail: paul.gill@ucl.ac.uk
GILL ET AL.
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LONE ACTOR MOTIVATION AND BEHAVIOR 435
... In a study based on a sample of lone-actor terrorists from Europe and the USA, Gill et al. (2014) reported that the individuals in the sample were between 15 and 69 years of age, with a mean age of 33 years. In line with what has been reported above, they conclude that these individuals were older than other extremists, and that many, but not all, were socially isolated. ...
... Within the category that the authors call "group-actors" (where the majority are likely to be actors within terror cells) a very low share of the offenders suffered from mental disorders, while disorders were more prevalent among lone dyads (i.e., two individuals conducting terrorist acts together; Corner et al., 2016). Another important observation is that lone actors displaying mental disorders still can have rational motives and act in a goal-oriented fashion (Borum, 2013;Gill et al., 2014). ...
... But the offender can also have personal motive, such as a real or perceived indignity" (Swedish Security Service [Säpo], 2020). Note that this definition includes not only individuals that have perpetrated terrorist-related acts but also those assessed to pose a threat, in line with several other studies in the field (Ellis et al., 2016a;Gill & Corner, 2017;Gill et al., 2014;De Roy van Zuijdewijn & Bakker, 2016). ...
... instead of "missing" (Drysdale et al., 2010;Fein & Vossekuil, 1999;Freilich et al., 2014;Gill et al., 2014;Silver, Horgan, & Gill, 2018;Vossekuil et al., 2004). This approach has been used in prior research examining similar forms of extreme violence including targeted violence affecting institutions of higher education (Drysdale et al., 2010), attempted assassinations of public figures (Fein & Vossekuil, 1999), lone offender terrorists (Gill et al., 2014), and fatal school shootings (Vossekuil et al., 2004). ...
... instead of "missing" (Drysdale et al., 2010;Fein & Vossekuil, 1999;Freilich et al., 2014;Gill et al., 2014;Silver, Horgan, & Gill, 2018;Vossekuil et al., 2004). This approach has been used in prior research examining similar forms of extreme violence including targeted violence affecting institutions of higher education (Drysdale et al., 2010), attempted assassinations of public figures (Fein & Vossekuil, 1999), lone offender terrorists (Gill et al., 2014), and fatal school shootings (Vossekuil et al., 2004). Parkin and Freilich (2015) argue that in many of these cases, if no information is found, "no" should be the default position. ...
Thesis
This study examines the reality and news media coverage of all mass shootings in the United States from 1966 to 2016. It employs agenda-setting and framing theoretical frameworks to determine the social construction of mass shootings via the mass media. The project uses open-source data to create a comprehensive list of mass shooting incidents. It then identifies all published New York Times articles on each incident. The study summarizes both the reality of the social problem (i.e. incidents) and the news mediated reality (i.e. New York Times). Next, this dissertation conducts a media distortion analysis to determine the perpetrator, motivation, and incident characteristics influencing media selection, prominence, and framing. The purpose is to illustrate the media’s social construction of mass shootings that in turn shapes public perceptions, political discourse, and public policies. The study concludes by highlighting the findings and implications for scholars, practitioners, policy-makers, media outlets, and the general public.
... The first issue is the sheer number of "indicators" that could be used to identify "risk." For example, Gill et al. (2014) identified over 100 potential VE risk factors. The second issue (linked to the first) is base rates; in that we are currently unaware of the base rates of these indicators in non-VE samples and nonviolent VE samples. ...
... actor and the nature of their engagement (Horgan, 2019). Thus, while involvement in VE was originally approached in simplistic terms, these attempts to profile VE offenders have given way to approaches that differentiate those who become involved in VE offending, both across different types of terrorism (religious vs. extreme left or right) and between different types of actor (Gill et al., 2014;Gill & Horgan, 2013;Gruenewald et al., 2013aGruenewald et al., , 2013bHorgan et al., 2016). Interestingly, this has led for calls to increase the nuance with which we approach issues such as risk assessment. ...
... The codebook contained 197 questions, covering; early life experiences, mental health problems, recruitment, roles and experiences whilst engaged, disengagement, post-disengagement experiences, and stressors. These questions were derived from previous codebooks used for open source data collection (Gill, Horgan, & Deckert, 2014), autobiographical data collection (Altier et al., 2012), and literature on terrorist engagement and disengagement (Altier et al., 2017;Borum, 2010;Gill & Corner, 2017;Horgan, 2009aHorgan, , 2009bReinares, 2011;Silke, 2003;Taylor & Horgan, 2006). ...
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Forensics has become an essential part of the disclosure of criminal evidence. A bioinformatics approach in the form of DNA forensics and digital forensics can be a good combination in disclosing digital-based criminal evidence. This study explains how the role of bioinformatics through the digital approach can be a means of forming new approaches in integration with digital forensics, called cyber-bioinformatics. Despite many hopes and challenges ahead, it does not rule out the possibility of criminal cases related to the privacy of human genomic data, so it proposes a new hypothesis, "cyber-bioinformatics." The role of cyber-bioinformatics is very central in this regard.
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