Paul Gill said ‘lone actor’ terrorists generally leave clues in planning their attacks and also tend to tell someone what they are going to do – all of which provides opportunities for intervention.
Irish academic Dr Gill, based at University College London (UCL), said the traditional law enforcement model needed to expand to a “multi-agency” approach.
His comments come as jihadist terrorism returned to France again yesterday after an 84-year-old priest Fr Jacques Hamel had his throat slit by two knife-wielding attackers, who also seriously hurt a nun.
The outrage in Rouen, which was claimed by Islamic State (IS), comes less than a fortnight after the Nice massacre and follows a week of attacks in Germany, one of which was not jihadist.
While one of the Rouen attackers was on the French terror watch-list, the other attackers were not on the radar of security services.
Dr Gill, who has conducted extensive work on terrorism for US, EU, and British funding bodies, said his “big worry” was that the attacks would spark violence by the far right —which, he said, would “play into the hands of IS”.
The senior lecturer in crime and security at UCL conducted a five-year study of 110 cases of lone actor —also known as lone wolf — terrorists.
“Generally, somebody knows something,” said Dr Gill, author of Lone-Actor Terrorists. “Other people become aware that they have adopted an ideology, that they have a grievance, against society or some target.”
He said that, in 60% of cases, the suspects “leaked specific information” about the attack.
“They become so fixated on what they are going to do, they end up telling people or they don’t want to be a lone actor and tell a friend or family member and ask do they want to come on board,” he said.
The lone wolf attacks could turn into so-called ‘dyad’ attacks, of two assailants, as in the cases of the Charlie Hebdo and Lee Rigby attacks, and seemingly in Rouen yesterday.
Dr Gill said the terrorists also often tell other people their plans because “they want people to know why they did it”.
He said the issue of how this information could be shared with police and security agencies was the “64 million dollar question”. He said the issue was known for decades as the ‘Bystander Effect’ in psychology circles — where a person sees something but will not communicate it.
He said fellow Irishman, US-based John Horgan, had conducted research among at-risk people in an area affected by radicalism.
Asked would they pass on information about someone being radicalised, the answer was “overwhelmingly ‘No’”.
Dr Gill said those interviewed said they would not want to get someone into trouble.
“The key is that this is not just a police or criminal justice route, but collaborative, with social workers, mental health practitioners, community leaders, and imams. It needs to be co-ordinated.”
Dr Gill said each person will have “different needs and different drivers”.
He said the required approach would need some type of “multi-agency structure”, not dissimilar to child protection services.
Dr Gill said “the differences” of lone actors defined them, as there was “no one pathway”.
His research found that 40% of lone attackers had mental health issues, compared to 25% in the general population. In addition, the severity of disorders were different, with significantly higher cases of delusional disorder and schizophrenia.
However, he stressed that there were “loads of other factors”, including breakdown of family or personal relationships, grievances or loss of a job.
Dr Gill said the role of religion, as with all factors, varied, with some very devout and others “quite illiterate” religiously.
He said that, traditionally, security services would monitor communications of suspects, but for lone attackers it was more difficult, as they typically radicalised and planned attacks by themselves.
He said what was key was “spotting the planning process”, such as the purchase and handling of materials, such as bomb parts.
“Generally speaking, it’s not spontaneous. It’s not a flick of a switch: Often there is a big build up,” said Dr Gill.
He said the most difficult cases to spot were those such as the Bastille Day attack on Nice, the Wurzburg train attacker, and now Rouen, where knives, axes, or trucks were used.
Dr Gill said Ireland should not think this was just an issue for other European countries: “We know for a fact that Irish citizens have gone over as foreign fighters. At some point, if it hasn’t already happened, they will come back.
“Even if it’s a small number, it only takes one person.”
He said Irish fighters could have built up connections with jihadists from other parts of Europe.