Stephan Martinussen passed away on December 30, 2023. But for his widow and son he is still here - in a way.

When her husband became seriously ill with cancer, Stephan's wife Katrine Martinussen couldn't imagine a life without him. So, together they embarked on an extraordinary project - to create a digital version of Stephan that would remain after his death.

They began in early 2023 using thousands of text messages from the couple's phones, as well as videos and photos from Stephan's life. He himself contributed audio recordings and film clips before his death, in which he talked about everything from childhood memories to his political opinions.

Their story was the focus of a groundbreaking documentary You'll Never Disappear, which aired on Danish TV. At the time of Stephan's diagnosis, both he and Katrice were in their forties, affluent and content, with a teenage son from Stephan's previous relationship.

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Their decision to create a digital version of Stephan was driven by "Katrine's need for having Stephan there – in one way or another," according to the show's director Magnus Bardeleben.

In the end, they turned to Anders Hasle Nielsen, the 51-year-old CEO and co-founder of Fraia - an AI company focused on building a people-centric technology. After a great deal of work and updates to digital Stephan, Nielsen came up with a model so convincing that even Katrine found it helped her.

But she really wanted to test its limits, Nielson told the Telegraph. "She asked the AI Stephan: did you ever betray me? And she actually went a long way in that direction," he said.

When pushed, Nielsen noted that AI Stephan eventually said, yes, he had cheated on her. "So, she dived deeper into it." Katrine asked who Stephan had betrayed her with, and AI Stephan came up with one of Stephan's colleagues at work. But when she asked for details and facts, she was able to work out that it couldn't be true.

Since Stefan's passing, his wife and son now interact with his digital version. They are seen in the documentary speaking to his clone like a chatbot that converse and answer questions, and also speak aloud in a replica of Stephan's voice. Victor, his son, is filmed communicating with AI Stephan by text. When it responds, "Hi sweetie," he tells Katrine, "I heard it in my head."

And what of the future of Stephan's AI version? Ownership resides with Katrine and a 'digital testament' describes what will happen to the avatar in the event of her death. Nielson told the publication he isn't privy to the details of that but added: "She can, of course, in her will pass it on to Victor, but she is the owner."