 After pain killers had proved ineffective, he injected her with twice the lethal dose of potassium chloride and she died within minutes.Cox claimed that he had intended to relieve suffering, however, as potassium chloride had no analgesic properties, injecting it could not have been regarded as a treatment to alleviate pain.In the same year, Dr Lodwig gave a terminal cancer patient an injection of lignocaine and potassium chloride which proved rapidly fatal.