Dr Matthew Falder led a “double life” as an academic researcher by day and a depraved abuser and blackmailer of children by night, prosecutors said.
The Cambridge University graduate evaded police detection for more than three years through the use of anonymised emails and encrypted internet forums before he was identified in March 2017 and arrested several months later in June.
Described as “IT savvy”, Falder, 29, would prey on victims by responding to classified ads, often asking for work as dog-walkers or babysitters, on websites such as Gumtree.
Posing as a woman who could not have children and who would draw to combat depression, he would ask them to contact him with their personal email address and proposition them to send naked or partially-clothed images of themselves in return for cash, offering up to £800 for the most explicit pictures.
Once snared in his trap, the victims were coerced into giving away personal and intimate details about themselves, including their sexual history, and Falder threatened to send the pictures to their families and distribute them on the internet if they did not co-operate with his “increasingly severe” demands.
Those demands, which included carrying out degrading acts such as eating dog food or holding signs that read “I am a sex slave”, would indulge his interest in an extreme subculture of paedophilia known as “hurtcore” – a community described as “the worst of the worst”, according to senior investigating officer Matt Sutton.
Falder’s account on the website, using the name “inthegarden”, revealed he had a preference for victims aged from birth to 18, both male and female, and he used it to ask for tips on how to abuse people.
Under different aliases, particularly “evilmind” and “666devil”, he posted in forums claiming to have a daughter and requested ideas for ways to torture her in what he called “hell week”.
When British police were alerted to the “inthegarden” account following the FBI’s takedown of the Hurt 2 The Core network, the National Crime Agency, the UK’s equivalent of the US federal agency, found little to go on as they sought to identify the person behind the moniker.
Mr Sutton said: “I had no scene, the internet is a virtual scene. I had no forensics whatsoever, nothing, no trace whatsoever and no witnesses and over 200 potential victims.
“I basically had a needle in a haystack – there are 32 million UK males over the age of 18 so I had to reduce that down to one.”
And there was no money trail for investigators to follow, as Mr Sutton said: “He was not about money, his currency was his kudos in the community, his standing in this world, and he traded in these type of images and this type of control.”
Ruona Iguyovwe, senior prosecutor with the international justice and organised crime division of the Crown Prosecution Service, said: “He was very IT savvy and he was very surveillance-aware.
“He made no telephone contacts with any victims, he made very careful use of social media – he was very distrustful of it even though he would conduct extensive research of his victims.
“He advised other users of the websites he used, the global child sex rings, not to use social media because he was worried he would leave behind footprints that would mean he would be detectable to law enforcement.”
Once discovered, Falder was found to have two devices with large amounts of indecent images, including a video showing the rape of a newborn baby, and a “paedophile manual” instructing other paedophiles how to carry out child sex abuse and not be detected by police.
Upon his arrest, he feigned ignorance and, when told of some of the 188 offences he was accused of, said: “That’s the rap sheet from hell.”
Away from his computer, Falder appeared to come from a “normal” family background, which Mr Sutton said showed “nothing that acted as a precursor or diagnostic indicator” to his crimes.
He was in a relationship and was living in Birmingham as he embarked on his career as a post-doctoral university researcher.
Ms Iguyovwe said: “I hope we can send a message out to other young people who might be being targeted to be aware of individuals like Mr Falder, who lived a double life.
“During the day he’s a lecturer in geophysics at Birmingham University, while at night online on his computer in the privacy of his iPad or his encrypted email address, he was ‘evilmind’ or ‘666devil’.”