Image copyrightGetty ImagesImage caption Mr Hutchins has been detained in the US since his arrest last August The British cyber-security expert credited with thwarting a major ransomware attack is attempting to prevent a phone call transcript being used against him in the US courts.The document quotes Marcus Hutchins as saying that he wrote code for an unidentified third-party, who then used it to make bank-hacking software.Mr Hutchins has been accused of creating and distributing the password-stealing malware Kronos.He has denied the charges.The Ilfracombe, Devon-based researcher rose to prominence a year ago when he halted the Wannacry ransomware attack that had caused havoc within the NHS as well as locking users out of other computers across the world.However, Mr Hutchins was arrested three months later by the FBI after attending cyber-security conferences in Las Vegas, at which he had been lauded.On Tuesday, prosecutors filed the call transcript along with a two-hour FBI interview, a day ahead of the latest hearing into the case.Mr Hutchins's lawyers are now seeking to have the evidence ruled inadmissible.They say he had been "sleep-deprived and intoxicated" at the time and had been "coerced" into a confession."So, I wrote code for a guy a while back who then incorporated it into a banking malware," Mr Hutchins is quoted as saying during the phone call after his arrest."So, they have logs of that, and essentially they want to know my part of the banking operation or if I just sold the code on to some guy."Once they found I sold the code to someone, they wanted me to give them his name, and I don't actually know anything about him."Mr Hutchins is also quoted as discussing paying off a 5,000 debt by passing on "compiled binary" of the code.The debt is explained by the loss of some Bitcoin digital currency that he had been looking after for someone else."I think the coding part I was less than 18, but I think giving him the binary I might have been older than 18," Mr Hutchins is said to have added."I knew it was always going to come back, I just didn't think it would be so soon."