Washington - The death of Liu Xiaobo is a catastrophic loss for China and the entire world, and his contributions to human rights should never be forgotten, members of Congress said during a hearing on Friday that turned into a memorial for China's most prominent political prisoner.Liu died Thursday of liver cancer after spending nearly nine years in custody. A House hearing had been scheduled to examine his health and detention. The news of his passing the day before prompted praise for his life's work in advancing liberty and due process as well as condemnation of the Chinese government for its treatment of Liu and his wife, Liu Xia."No nation should be judged entirely by crimes of the past, but this crime, the death and silencing of Liu Xiaobo, should follow the Chinese Community Party like an unwashable, permanent stain," said Chris Smith, chair of the House Foreign Affairs subcommittee on Africa, Global Health, Global Human Rights, and International Organisations.Two pictures were positioned prominently in the hearing room - one of Liu and the other of an empty chair with his Nobel Peace Prize placed where he would have been sitting if he had been allowed to attend the 2010 ceremony. Liu was serving an 11-year sentence for incitement to subvert state power. He died at the age of 61.House Minority Leader Nancy Pelosi and Smith noted that they had attended the award ceremony. Pelosi called Liu "one of the great moral voices of our time".Liu rose to prominence during the 1989 pro-democracy protests centred in Beijing's Tiananmen Square, and became one of hundreds of Chinese imprisoned for crimes linked to the demonstrations after they were crushed by the military. It was the first of four imprisonments.Efforts not in vainHis last was for co-authoring Charter 08, a document circulated in 2008 that called for more freedom of expression, human rights and an independent judiciary."Liu's efforts were not in vain," said Ed Royce, chair of the Foreign Affairs Committee. "His sacrifice and death while in the custody of the Chinese government while serving an unjustified 11-year prison sentence has shined a light on the sad state of human rights in China."The panel heard from academics and activists familiar with Liu's work. They described the suffering that he endured in prison."Even on his deathbed, he had no freedom to leave his last words. Now that he is gone the world will never know," lamented Yang Jianli, who participated in the demonstrations for democracy in Tiananmen Square and also served five years in prison in China.The lawmakers and witnesses wondered how his legacy would and could be perpetuated.Perry Link, a professor at the University of California at Riverside, raised the question of whether Liu's efforts were in vain. He said no, but the answer was difficult."Two hundred years from now, who will remember the tyrants who sent Mandela, Havel and Suu Kyi to jail? Will the glint of Liu Xiaobo's incisive intellect be remembered, or the cardboard mediocrity of Xi's?" Link asked, a reference to Chinese President Xi Jinping.That elicited a response from Pelosi, who said, "Dr Link, I don't think it's going to take 200 years, I think right now is the contribution; the legacy of Liu Xiaobo will certainly eclipse the authoritarians of China.Smith held a moment of silence for Liu at the conclusion of the hearing.