Lawyers representing Associated Newspapers, which also publishes the Mail on Sunday, challenged a ruling on the admissibility of anonymous evidence at London's High Court before Lord Justice Toulson, Mr Justice Sweeney and Mrs Justice Sharp.
But Lord Justice Toulson, Mr Justice Royce and Mrs Justice Macur unanimously agreed it would be wrong to depart from the long-established legal position that "voluntary euthanasia is murder, however understandable the motives may be".