It can never be certain that terror offenders who attend deradicalisation programmes have been “cured”, psychologist Christopher Dean has said.
Mr Dean is behind the UK’s main deradicalisation programme for such offenders.
London Bridge killer Usman Khan attended a deradicalisation programme after being released on licence.
Khan was a convicted terrorist who had been a member of an al Qaida-inspired group that plotted to blow up the London Stock Exchange.
The 28-year-old killed two people and injured three others in a knife rampage before being shot dead by police in November.
He had been released from prison on licence in December 2018, by which time Khan reportedly appeared to be responding to rehabilitation.
Speaking on BBC Radio 4’s Today programme on Thursday, Mr Dean said some offenders who take part in his Healthy Identity Intervention scheme regress afterwards due to complex reasons such as who they mix with.
“The two main aims of healthy identity intervention are primarily to try and make individuals less willing or prepared to commit offences on behalf of a violent extremist group cause or ideology,” he said.
“If we can reduce someone’s relationship or identification with a particular group, cause or ideology, that in itself may have an impact on whether they’re willing to offend or not.”
Mr Dean said some offenders he worked with needed 20 or more sessions to show signs of positive change.
“We see some individuals who may have been part of a group for many years or have been invested or identified with the cause for many years. [Leaving that group] is an incredibly difficult thing to do,” he said.
He added that there is no guarantee of success.
“I think we have to be very careful about ever saying that somebody no longer presents a risk of committing an offence. I don’t think you can ever be sure,” he said.
“We have to be very careful about saying someone has totally changed or has been cured.”