A GP accused of trying to murder his mother’s long-term partner sparked fears he had poisoned him with the chemical weapon ricin, jurors heard.

Dr Thomas Kwan, 53, denies attempted murder and an alternative charge of causing grievous bodily harm with intent but has admitted administering a poison to Patrick O’Hara.

Peter Makepeace KC, prosecuting, told Newcastle Crown Court that police found “an array” of chemicals such as arsenic and liquid mercury in the GP’s garage at his home in Ingleby Barwick after he was arrested.

(Image: TERRY BLACKBURN) Mr Makepeace said: “Also recovered from the garage were a significant quantity of castor oil beans and coffee filters, what significance could that have you may ask?

“Well, recovered from Mr Kwan’s office, in the house itself, was a recipe for manufacturing ricin from castor beans, using filtration.

“Ricin, many of you will know, is a highly toxic poison and a scheduled chemical weapon.

(Image: TERRY BLACKBURN) “Whilst Mr Kwan refused to answer any questions relating to the alleged offence against Mr O’Hara in interview, he did give some answers to an interview designed to understand the risk officers were under in searching his garage and the wider risk to neighbouring properties, given the chemicals involved.

“He told officers all the chemicals were safe provided they remained sealed and the officers should not open any of the containers.”

Mr Makepeace said medics were working to save Mr O’Hara, who had the flesh-eating condition necrotising fasciitis, and needed to know which poison had been used.

(Image: TERRY BLACKBURN) “The recovery of the castor oil beans in the garage of the accused together with the recipe for the production of ricin from castor beans found in his office, raised the very real possibility that the toxin injected was ricin,” the prosecution said.

Professor Steven Emmett, the Chief Medical Officer at the Defence Science and Technology Laboratories, which operates as part of the Ministry of Defence, was engaged to review Mr O’Hara’s condition.

The prosecution said the expert was still not sure which poison was used, but he did not favour ricin as the one used.

(Image: Terry Blackburn) Instead, he believed iodomethane, used in pesticides, was the chemical.

Analysis of Kwan’s phone showed he searched “iodomethane” on the internet 97 times in the run-up to the attack.

Mr Makepeace said Professor Emmett formed the view that iodomethane was less obviously detected by medics than the other chemicals found in Kwan’s garage.

“In other words, if you want to not only inject a substance that causes necrotising fasciitis into a person but make it as difficult as possible for the medical team to identify the cause and treat the illness, iodomethane is the one to pick from the many substances available to Mr Kwan,” he said.

Police searches of his computers also revealed he had a PDF on how police conduct murder investigations, a video on how to produce iodomethane, an eBook titled Forensic Science and Medicine: Criminal Poisoning and a copy of The Terrorist’s Handbook.

Recommended reading:

Get more from The Northern Echo with a digital subscription. Get access for one month for just £1, or get 30% off an annual subscription with our latest offer. Click here.

Officers also discovered that Kwan had placed spyware on his mother’s computer allowing him to read her emails and use her laptop’s digital camera to watch her and Mr O’Hara as they went about their business, the court heard.

Kwan used the spyware to monitor his mother’s financial dealings, Mr Makepeace said.

He also set up a shell business to obtain chemicals from legitimate suppliers, using his surgery as the delivery address, the court heard.

The trial continues.