This CREST guide focuses on the insights criminology can provide into terrorist decision-making. It looks at what terrorists do and how they do it.

Key questions

  • How do men and women decide to commit an act of terrorism?
  • Do they plan wisely?
  • How do they choose their targets?
  • How do they evaluate the risk of a single operation?
  • How is decision-making affected by the emotions felt during the planning and operational phases?
  • Can law enforcement be usefully informed by what we know about the behaviours of those who commit other kinds of crimes?


Terrorist actions are rational. Deliberate choices are made regarding the target, weapons, clustering attacks, and potential victims. The level of planning may depend on the complexity of the attack, the appearance of sudden, unanticipated opportunity, or perceptions of law enforcement. Sometimes planning is extensive.

“The priority should be to develop and plan … the information which unit commanders would need to mount successful operations against enemy personnel or to sabotage enemy installations … I issued instructions to Intelligence Officers (IO) that they should study the daily and local newspapers carefully, and indeed read every serious magazine and periodical they could lay their hands on …”  (Member of the Provisional IRA).

Sometimes attacks are spontaneous and ‘planning’ develops only in the course of daily activities.

A Weathermen Underground attack on a United Fruit warehouse was planned on the same day it took place because one of the group passed “it lots of times”. Over the course of the previous couple of days, he had “been checking it out” in more detail for the purpose of an attack, observing it “deserted after six o’clock at night”.

A member of the Provisional IRA recalled an open-back British Army jeep driving unaccompanied into their stronghold.

At this time the British Army would never come in unless heavily armed and in armoured cars. This particular day we weren’t expecting anything like this … Here was something that just came out of the blue … We were so confident and in such control of the area at that time that instinct took over: ‘There’s a target’ and ‘Hit it.’”

Similar variance is found for other kinds of crimes. Sometimes planning is extensive, especially for more complicated crimes (e.g. bank robberies are planned more often than muggings). Other times crimes are more spontaneous and the same criminal may sometimes plan and sometimes not.

Choice of target

The types of targets attracting terrorist attention are typically highly guarded.

Anders Breivik considered assassinating a member of government but decided not to because such individuals are often well-protected. From an operational perspective, he saw Utøya Island as ideal because it was “isolated” and “police would have problems” accessing the site.

Whether or not to attack sometimes depends on perceptions of the effectiveness of security. Eric Rudolph described the security in the Atlanta Olympics Park:

Hundreds of security guards and cops patrolled the park. They eyeballed me going through the entrances. But there were no metal detectors, and bags were searched selectively. After sundown, the crowds grew enormous … Security at the park became overwhelmed. They stopped searching bags altogether, and the entrances flew wide open. I knew then that I could smuggle in a bomb.

Whether or not to attack sometimes depends on perceptions of the effectiveness of security.

Although variable, other criminals report assessing informal/natural surveillance, formal surveillance, CCTVs and alarm systems. They also may be more affected by how the security is deployed than whether or not is it present. Third parties not involved in the actual crime sometimes spot opportunities and pass this information to an eventual offender. This has been noted for captive takers, burglars, robbers, and drug dealers.

Risk assessment

What distinguishes terrorism from other criminal acts is that it is deployed for its impact not just on the victims of an attack but on the general public; it is considered an effective political strategy. Public impact, therefore, is part of the cost/benefit analysis.

According to Ann Hansen, of Direct Action, there was ambivalence about whether or not to attack the Cheekye-Dunsmuir electrical line in Canada.

We did not want to sabotage the project after it went on-line, because we wanted to avoid causing power blackouts to residential areas. Ordinary people would feel the brunt of the action if hospitals, traffic lights, or other essential services were shut down, and we didn’t want that.

Perceived consequences matter and perceptions that there is a greater risk sometimes leads to both reconnaissance (which increases vulnerability) and attempting larger attacks. Multiple targets may be considered.

Ann Hansen of Direct Action noted that the group “decided to keep the actions small and simple so that people could get involved without having to fear serious prison time as a consequence.”

The Atlantic City bomber, Eric Rudolph, said, “I had spent a week earlier that month casing … There was no hideout near the target, no place of concealment where I could sit and scope it out, so I did my scouting on the move. After parking a mile away, I made three passes … each day. I strolled past it at different times of the day, approaching from a different angle and wearing a slightly different disguise on each pass.

terrorist decision making intoxication

An IRA member reported that “operations were becoming increasingly difficult and dangerous, with … forensics, surveillance, ubiquitous helicopters, the security forces’ more sophisticated understanding of IRA methods, quicker reaction by police and army, fewer opportunities because of better fieldcraft by the security forces. There, while operations became less frequent, they tended to become larger set-pieces …

A member of the Weather Underground reported that “we agreed to investigate other targets as well … One team went to each of the possible sites to do reconnaissance … … The conversation focused on which of the targets we had investigated were feasible. Then we discussed the logistical details required for each action.

Cost-benefit analyses also differ among other criminals. For example, inexperienced commercial robbers pay more attention to potential benefits at the expense of focusing on risks. There may be a general unawareness or blindness to risk amongst some offenders due to intoxication or because co-offenders actively downplay the risk. Previous successes lead to downplaying immediate situational risks. Sometimes risk is accepted and circumvented by predetermined plans to display an illusion of normalcy.

Does fear deter?

In their own words, men and women who have committed acts of terrorism report fear and anxiety:

“For days beforehand, the nerves would burn the inside of your stomach. There would be plenty of sleepless nights spent tossing and turning as you went over and over what was going to happen.”

“There was nothing to show I had been rumbled, but some inborn sense of danger was whispering warnings in my ear. I forced myself to go on, repeating silently to myself ‘Don’t panic!’”

Fear sometimes is ameliorated by drugs. Upon being apprehended, Breivik announced that he had taken a combination of ephedrine, caffeine, and aspirin in order to enhance his performance.

Feelings of fear, nerves, stress, tension, worries, apprehension, anxiety, physical sickness and uncertainty are also reported among various kinds of criminals, including street robbers, first-time sex offenders, card fraudsters, thieves, muggers, and armed robbers. These individuals also self-report substance abuse during the crime commission in order to help overcome fear and nervousness.

Implications for law enforcement

The successful conduct of a terrorist attack requires not only a motivated offender, but also a lack of capable guardianship and the presence of an appropriate victim. In other words, it needs an opportunity.

As can be seen, terrorists make cost-benefit decisions in much the same way as other criminals. The field of crime prevention evaluation shows that we should focus on the settings in which offences take place rather than underlying motivation or criminal disposition of the individual actor. Reducing the opportunities for terrorism via environmental design is therefore a valid and worthwhile pursuit.

Reducing the opportunities for terrorism via environmental design is therefore a valid and worthwhile pursuit.

Each type of terrorist attack, be it a vehicular assault or a bombing, depends on the crystallisation of multiple opportunities. In turn, each specific attack type offers its own set of particular opportunities that can be manipulated with the intention of impacting the terrorist cost-benefit calculus. Such endeavours are target hardening, controlling access to facilities, and controlling access to the necessary weapons. Such actions include extending guardianship, assisting with natural surveillance, reducing anonymity, utilising place management, strengthening formal surveillance, and concealing or removing potential targets.

  • Fear is a factor in all phases of a terrorist attack, just as it is a factor in other kinds of crimes. Interventions that aim to increase such fear therefore should be beneficial.
  • The sources of fear include fear of detection by police/security and fear of detection by conscientious bystanders. Making these more obvious should increase this fear.

Interventions that hide the security details from the general public should increase uncertainty and either lead to full disruption or the planner taking ever greater risks to minimise their uncertainty. Fear of the ‘unknown’ is also paramount. Such feelings can be multiplied if the would-be offender believes the ability of security to detect suspicious behaviour is high. Interventions that highlight, embellish and evidence the ability of security, staff, and/or bystanders to detect suspicious behaviour should have a positive net benefit.

Read more
  • Gill, P., Marchment, Z., Corner, E. and Bouhana, N. (2020). Terrorist decision making in the context of risk, attack planning, and attack commission. Studies in Conflict & Terrorism, 43(2), 145–160.
  • Marchment, Z. and Gill, P. (2019). Modelling the spatial decision making of terrorists: The discrete choice approach. Applied geography, 104, 21–31.
  • Gill, P., Corner, E., McKee, A., Hitchen, P. and Betley, P. (2019). What do closed source data tell us about lone actor terrorist behavior? A research note. Terrorism and Political Violence, 1–18.
  • Robinson, A., Marchment, Z. and Gill, P. (2019). Domestic extremist criminal damage events: behaving like criminals or terrorists?. Security Journal, 32(2), 153–167.
  • Marchment, Z. and Gill, P. (2020). Spatial Decision Making of Terrorist Target Selection: Introducing the TRACK Framework. Studies in Conflict & Terrorism, 1–19