Terrorist offenders should take lie detector tests, according to a review into UK government failures that allowed a released prisoner to stab fatally two young people at a rehabilitation conference last year.
A review commissioned following last year’s attack near London Bridge has made 45 recommendations.
Cambridge University graduates Jack Merritt, 25, and Saskia Jones, 23, were stabbed to death last November by Usman Khan.
Khan, who had been released early from serving a 16-year jail sentence for plotting to blow up the London Stock Exchange, was attending a prisoner rehabilitation event at the time.
In a review of the multi-agency public protection arrangements (Mappa), barrister Jonathan Hall QC said lie detector tests could help the authorities discover whether a released terrorist was a threat.
“Polygraph testing is not a means of predicting whether an offender will reoffend. It is a useful means of gathering information which is relevant to the assessment of risk,” he said.
“Polygraph testing is a sensible additional tool for obtaining information relevant to the risk posed by terrorist offenders. Polygraph testing for terrorist offenders should be adopted.”
Britain's Ministry of Justice says the government is currently legislating to force terrorism offenders to take lie detector tests.
The report also revealed there needed to be “wider sharing” of information between professionals and called for a "cultural shift" in how authorities shared information about people convicted of terrorism.
“There should be wider sharing with probation officers not only of specific intelligence but also of threat assessments and profiles; probation officers involved in assessing terrorist risk should be given some training in the principles of intelligence assessment,” he added.
Home Office minister Chris Philp said the authorities were working together to review the recommendations in the report.
"Jonathan Hall found that Mappa is a well-established process and did not conclude that wholesale change is necessary,” he said.
"He has made a number of recommendations on how the management of terrorists can be improved and the government, police and Prison and Probation Service have been working on changes in line with many of them."