THE HAGUE: For a moral victory, it was a bittersweet one. Denounced worldwide as the thugs behind the bulk of Bosnia's war crimes, Bosnian Serbs Tuesday were cast as the victims, detailing horrific scenes of gang rape, torture and murder at the hands of Muslim a nd Croatian prison officials for a hushed United Nations tribunal. The trial of three Muslims and one Croat is the first collective war crimes trial since the end of World War II and the first to judge rape as a war crime. Seventy-six witnesses will make the trip from Yugoslavia to testify before the U.N. tribunal about conditions in the Celebici concentration camp, set up by Muslim authorities at the beginning of the Bosnian war as a detention center for Serb prisoners. Fourteen inmates are thought to have died in the camp, including one man who had a Muslim party logo nailed to his head. The indictment charges that, aside from various forms of sexual violence, prison guards also regularly beat inmates with steel cables, wrapped them in lighted fuses and then left them to soak in vats of water. While the gruesome accounts did not appear to faze the four defendants, who spent their time doodling with pencils or rolling their eyes in disdain, the trial was not without its surprises. Branislav Tapuskovic, the ethnic Serb lawyer for Croatian defendant Zdravko Mucic, claimed that his client had taken the job as camp commander solely out of a humanitarian desire to increase food supplies and release Serb prisoners. "Mucic was trying to help the people . . . he was not really in charge," argued Tapuskovic. "Conditions in the camp were not meant to make people suffer." Instead, Tapuskovic maintains, guilt for the Celebici atrocities lies squarely on the heads of the three Muslim d efendants: Zejnil Delalic, a Muslim military commander thought to have established the camp, Hazim Delic, the camp's deputy commander charged with four murders, and camp guard Esad Landzo, who is accused of five slayings and multiple torture sessions. If found guilty, the four men face life in prison. For Serbs outraged that Bosnian Serbs so far have received the bulk of the tribunal's 74 indictments, the comeuppance would arrive none too soon.