A PRIVATE detective who posed as a journalist in order to register as a doctor using faked Australian and New Zealand qualifications, yesterday started an eight-month prison sentence. Yu Kin-chiu, 27, described by his defence counsel as a curious person who wanted to know more about other people's jobs, told the District Court it was ''fun'' to send the forged qualifications to the Hongkong Medical Council in a bid to be registered here. Yu had obtained the documents after writing to the West Australian and New Zealand medical boards saying he was a journalist writing a story about forged medical certificates. His defence was rejected by Deputy Judge Chow, who told Yu he had not ''come clean'' when telephoned by the Medical Council, which wanted to verify his application for a medical practitioner's licence. Sentencing Yu, Deputy Judge Chow said he did not think Yu's actions were at all amusing, and that he had gone to too much effort to make him believe it was simply being done as a joke. Yu was convicted on six counts of forgery and two of uttering forged documents, including a photocopy of a University of New South Wales Bachelor of Medicine and Bachelor of Surgery degree certificates. Although he accepted defence counsel Ms Susanna Lee's mitigation that Yu had never intended to practise as a doctor and that no harm was done to the public, his offences were still serious. For the prosecution, Mr Andrew Raffell said on September 19 the Hongkong Medical Council received an application for a medical practitioner's licence in Yu's name. With it was a medical school graduation certificate, a registration from the medical boards of Western Australia and New Zealand, certificates of good standing from both, and the $750 fee for a Hongkong licence. When the Medical Council called him at his flat in Shamshuipo he did not admit the truth, instead telling the caller ''Dr Yu'' was in Australia.