An IT worker is facing a life prison sentence for the murder of a married couple who he poisoned with fentanyl after creating a gallery of online personas to manipulate them.

Luke D’Wit, who befriended and worked for Stephen and Carol Baxter, later changed their will to make him a director of their shower mat company.

The 34-year-old had pretended to be a doctor from Florida and members of a fake support group for the thyroid condition Hashimoto’s, which Mrs Baxter suffered from.

Mrs Baxter, 64, and her 61-year-old husband were found dead at their home in West Mersea in Essex by their daughter Ellie on Easter Sunday last year.

D’Wit, of West Mersea, arrived soon after and described himself as a “friend” to a 999 call handler, before calmly giving a false account.

Prosecutors said he created a fake will on his phone the day after the Baxters were found dead, making him a director of their shower mat company Cazsplash.

Another fake persona – a solicitor – was used in connection with the new will, prosecutors said.

On Wednesday, D’Wit was found guilty at Chelmsford Crown Court of murdering the couple following a trial lasting more than a month.

He is due to be sentenced at the same court on Friday by judge Mr Justice Nicholas Lavender.

The couple’s daughter said in evidence that her parents believed D’Wit was “weird, but nerdy weird”.

She said he had initially been brought into their shower mat business in about 2012 or 2013 to “help build the website” before eventually coming round to their house “every day”.

Her brother, Harry, said afterwards that they “were all dolls in (D’Wit’s) dollhouse, victim to his manipulation”.

Detective Superintendent Rob Kirby, of the Kent and Essex Serious Crime Directorate, said outside court: “I have absolutely no doubt in my mind had he not been caught he would have gone on to kill further people.”