An IT worker who poisoned a married couple with fentanyl is feared to have killed his own father and grandfather.
Luke D'Wit, 34, was jailed for life with a minimum term of 37 years after using the opioid painkiller to poison Stephen and Carol Baxter at their £1million home in West Mersea, Essex.
Detectives are now exploring whether D’Wit was responsible for the death of his father, Vernon, who had been prescribed fentanyl before he was found dead in a chair at his nearby home in 2021.
As part of their review, detectives have also been re-examining how D’Wit’s grandfather died.
Essex Police said: “Up to the conviction and sentence of Luke D’Wit, our determined focus has been securing justice in relation to the murders of Carol and Stephen.
“As with any investigation of this magnitude, everything we have uncovered is being reviewed and should anything suggest this has been the case we will not hesitate to act.”
Detective Superintendent Rob Kirby previously told the BBC News, which broke news of the development, he could not rule out the possibility D’Wit had already killed others before being convicted of murdering the Baxters.
He had “absolutely no doubt” D’Wit would have committed further murders had he not been caught.
Det Supt Kirby described the killer as “one of the most dangerous men” he had seen during his career.
D’Wit, who befriended and worked for Stephen and Carol Baxter, created a gallery of fake personas to manipulate them in the two years before their deaths.
He pretended to be a doctor from Florida and members of a fake support group for the thyroid condition Hashimoto’s, which Mrs Baxter had been diagnosed with.
He later changed their will to make him a director of their shower mat company.
Mrs Baxter, 64, and her 61-year-old husband were found dead at their home 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, as Ellie was heard in distress in the background, Chelmsford Crown Court heard.
The judge, Mr Justice Nicholas Lavender, said he was sure that D’Wit “extracted the fentanyl from patches which had been originally prescribed for your father, who died in 2021”.
He said promethazine tablets were crushed into a powder.
He said D’Wit gave the drugs to the Baxters in a drink on April 7, which they took as they trusted D’Wit to prepare “supposed health drinks” for them.
The defendant cleaned up afterwards, the judge said, adding that “when the Baxters were unconscious, you took the macabre step of using an application on two mobile telephones to monitor them while you left the house for a time”.
The judge said that over the course of about nine years, D’Wit “became a close friend of the Baxters, who regarded you as a member of their family”.
Reading her victim impact statement in court, Ellie Baxter told how D’Wit “lied his way into our lives”.
She described him as a “man so manipulative he hacked his way into our lives over a decade ago, schemed and thoroughly planned my parents’ demise”.
She said her parents had “looked after Luke”, adding: “They just decided he was lonely, especially after Luke’s dad died.
“They took him under their wing and would let him join in.”
She said her mother was “completely brainwashed” by D’Wit, who posed as a doctor.
