An American man who ran a fraudulent suicide-by-post business has been convicted of posting a fatal dose of potassium cyanide to a Briton in an attempt to prevent him exposing details of the scam to the FBI.

A jury in Bangor, Maine, found Sidney Kilmartin, 54, guilty of of witness tampering, wire fraud, mail fraud and mailing an injurious substance which resulted in the death of Andrew Denton, 49, from Hull in on December 31 2012.

Kilmartin was acquitted of a charge of witness retaliation.

Mr Denton was one of a number of disenchanted customers who had been defrauded by a bogus mail order suicide business set up by Kilmartin.

But unlike others, he complained to the FBI and it cost him his life.

Kilmartin had set up his scam by posing as a goldsmith to buy 100 grams of potassium cyanide for $127.56 (£105) from a company which provided chemicals to industrial clients in September 2012.

He then sought out suicidal clients by posting on the website “wantdeathblogspot” that he had cyanide available.

Clients from around the world were invited to contact him by email on a dedicated Google account.

They were instructed to send wire payments via Western Union or PayPal on the understanding that they would receive the cyanide in return.