An international group of lawyers is planning a court challenge to the government screening process that determines which Vietnamese boat people are to be forcibly repatriated, a spokesman said today. ``We think that there are cases of persons who are genuine refugees who have fallen through the cracks in the process'' and were mistakenly classified as illegal immigrants, said David Clark, senior lecturer in political science at Hong Kong University. This British colony once considered all Vietnamese who arrived by boat to seek asylum as refugees eligible for resettlement overseas. But the government, facing a mounting influx of Vietnamese, decided in June 1988 to classify arriving boat people as illegal immigrants subject to repatriation unless they could prove they fled persecution in their Communist homeland. About 85 percent of the approximately 44,000 boat people who have arrived under the new policy are expected to face forced repatriation. The current screening process involves an interview with an immigration officer and gives the opportunity for one appeal. So far, 51 boat people have been forcibly repatriated and about 1,000 have gone back voluntarily. The London-based human rights organization Amnesty International earlier this week criticized the program, saying immigration officers often have scant knowledge of the situation in Vietnam and that translating services need improvement. The group of lawyers, which includes members from the United States and Britain, has selected nine boat people who were screened out by immigration officials and had their appeals denied. ``We have evidence in those cases that there were various defects'' in the process, said Clark. He added that the Vietnamese chosen for the case appear to have a good claim to being classified as refugees. The lawyers plan to go to the colony's High Court with their complaints in a few weeks to seek the overturn of the screening results, said Clark, who has taught administrative law in Hong Kong for 11 years. ``It will be a tough case to win,'' he said. ``The government will fight it tooth and nail.' If the High Court rules against the challenge, the lawyers' group can take the case to the Court of Appeal in Hong Kong and then the Privy Council in London. If that fails, the group may take action against the screening process through the European Commission of Human Rights. The impetus for the legal challenge came largely from Americans Arthur Helton, of the Lawyers' Committee for Human Rights; Janelle Diller, of the Indochina Resource Action Center, and Briton David Burgess.