BBC News found that London Bridge striker Usman Khan had participated in two counterterrorism programs that had not yet been fully tested to verify their effectiveness.
Khan, convicted of terrorism in 2012, Friday killed Jack Merritt, 25, and Saskia Jones, 23.
He had completed two rehabilitation projects during his eight years in prison and following his release.
The government says these programs are "under constant surveillance".
Three others were injured after the launch of Khan's attack during a prisoner rehabilitation event inside Fishmongers Hall near London Bridge.
Investigations into the deaths of Mr. Merritt and Ms. Jones were opened and adjourned Wednesday at the Old Bailey.
The court heard that both men died after being stabbed in the chest. The date of the full investigations remains to be determined.
London City's Chief Coroner, Alison Hewitt, also opened and suspended the investigation into Khan, who has died as a result of multiple gunshot wounds after being shot by police.
The investigation learned that Khan had gone on the scene to participate in group workshops.
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While in prison, Khan attended a course for people convicted of extremist offenses and, after his release, embarked on a program to tackle the causes. of terrorism.
The first course, followed by the Intervention Program for a Healthy Identity, was put on trial from 2010 and is now the main rehabilitation program for detainees convicted of drug offenses. 39; extremism.
Last year, the Ministry of Justice published the results of the research conducted as part of the pilot project, which revealed that it had been "positively perceived" by a sample of people who attended and animated the course.
However, the ministry has not yet completed its work to verify whether the system prevents recidivism or effectively attacks extremist behavior.
Nor was there an evaluation of the impact of the discontinuance and disengagement program, which Khan had participated in after his release last year.
Government officials pointed out that the mechanisms in place have not been functioning long enough to allow for the evaluation of results, but one spokesperson said that all programs related to offender behavior were constantly being reviewed.
The spokesperson said: "All of our offender behavior programs are continuously monitored, assessed and monitored to ensure they are effective in reducing reoffending and protecting the public."
The Home Office's "Information Sheet" on the Disengagement and Disengagement program contains eight "key" information.
But he misses the point: the program has never been evaluated. In other words, we do not know if it works.
The same goes for the Interventions for a Healthy Identity course. Although the Department of Justice has conducted a "process evaluation" to verify that the pilot version was working properly, we will not know for two years if it is producing results.
Thus, like many other projects on offender behavior, these schemes are essentially experimental.
Some say the only way to know if they are good is to try them. Others argue that the risks associated with such a practice are too high, evoking the once-lone sex offender treatment program, used for 25 years until research shows that it increases the risk of reoffending.
Rehabilitating convicted terrorists is as complex and difficult as it becomes – but a little more frankness and honesty is needed regarding the methods used.
A man who recently followed the same program of withdrawal and disengagement as Khan said that the London Bridge attacker "should not have been released from prison".
The man – who asked to remain anonymous – was acquitted of terrorism charges but was forced to carry an electronic tag.
Sending to Sima Kotecha on BBC Radio 4's Today show, he said: "One of my mentors came to see me at least twice a week.
"Over time, the authorities have noticed a change in me."
When asked why such mentoring worked for him but not for Khan, the man replied, "I wanted to make a change.
"Other people may think that [terror] is the only way because they have been radicalized and that's all they know. "
He added that "anyone can manipulate" when asked if people could convince their mentors that they have moved away from extremism.
He said, "I do not know his character, but everyone can handle it."
Khan, 28, was arrested in December 2010 and sentenced in 2012 to indefinite detention for the purpose of public protection, with a minimum term of imprisonment of eight years, after pleading guilty to aggravating the crime. have prepared terrorist acts.
He was part of a group inspired by Al Qaeda that was planning attacks in the UK, including the London Stock Exchange.
In 2013, the Appeals Court quashed the sentence by replacing it with a 16-year sentence and ordered Mr. Khan to serve at least half of that sentence, eight years behind bars.
Since his release from prison in December 2018, Khan lived in Stafford and was required to wear a GPS tag.
Khan was armed with two knives and was wearing a fake suicide vest during the attack on Fishmongers Hall in London on Friday.
Members of the public, including former delinquents from the conference, addressed him before being shot by the police.
Porter acted instinctively
Among the people praised for their courage during the attack was a porter, named Lukasz, who had tried to fight with Khan at Fishmongers Hall.
He issued a statement Tuesday through Scotland Yard, saying that contrary to some reports, he had used a post to attack Khan, while someone else was using a narwhal defense.
"The man attacked me, after which he left the building," he said. "A number of us followed him outside, but I stopped at the terminals of the bridge, stabbed him and later took him to the hospital. hospital for treatment. "
He said that he was "grateful" that he has now returned home.
"When the attack occurred, I acted instinctively," he said. "I am now managing the traumatic incident as a whole and would like the space to be set up confidentially, with the support of my family."
He wishes to express his condolences to the families who have "lost precious loved ones," he added, while extending his best wishes to "all those affected by this sad and unnecessary attack".
Two women were also injured in the attack. They remain in stable condition at the hospital.