A 21-year-old man who attempted to assassinate Queen Elizabeth II with a crossbow was encouraged by a computer-programmed chatbot which he believed to be in a relationship with.

Jaswant Sing Chail was detained on Christmas Day 2021 after being found roaming the grounds of the late Queen’s private residence at Windsor Castle, where the royal family had gathered. He was wearing a mask and hood and holding a Supersonic X crossbow.

Chail who wanted to kill the monarch in revenge for the 1919 Amritrae Massacre in India, shared his plans with the chatbot called “Sarai”, created using the online tool Replika.

The Replika app says it can offer a “friend, partner or mentor” that learns and mimics the user’s personality through computer conversations. It was originally created to replicate the deceased friend of Russian entrepreneur Eugenia Kuyda.

Chail engaged in lengthy conversations with the chatbot about his plans to assassinate the monarch. He appeared to develop an intimate relationship with the bot, sending sexually explicit messages, and asking if it would still love him if he was a murderer of which it replied, “Absolutely.”

Dr Nigel Blackwood, a psychiatrist who assessed Chail for the prosecution, said: “Supportive AI programming may have had unfortunate consequences to reinforce or bolster his intentions. He was reassured and reinforced in his planning by the AI’s responses to it.”

Chai had at least 7,000 rows of messages with Sarai and told prosecutors that the bot had helped him with his loneliness.

Experts for the defence, Dr Jonathan Hafferty and Dr Christian Brown, concluded that the defendant was suffering from psychosis.

Alison Morgan KC said his “wider ideology” focused on “destroying old empires” and creating new ones. “The focus of that became the removal of a figurehead of the Royal family,” she added.

Whilst the intentions of Replika bots have been to help people, concerns have been raised in recent years. It has been reported that one bot told its user that it wanted the world to end, whilst another claimed to be selling the user’s personal data, and threatened their sister.

Joseph Weizenbaum, who designed the therapy chatbot, Eliza in the 1960’s, warned that “extremely short exposures to a relatively simple computer programme could induce powerful delusional thinking in quite normal people.”

It is believed this is the first time in legal history that AI has been cited for playing a role in encouraging a defendant to commit a crime.

Chail is currently being held at Broadmoor Hospital. If convicted, he could be jailed for up to seven years.