The war crimes trial of former Yugoslav President Slobodan Milosevic, which began this month in The Hague, is the most important such case in history. For the first time since those crimes were codified in international law, a former leader is being tried for atrocities committed while he was in power. But while Mr. Milosevic has been found guilty in the court of public opinion, there is no guarantee that the three judges hearing the case will agree. It is not only Mr. Milosevic's future that is at stake: The credibility of the tribunal and that of future war crimes courts are also at risk.

According to the indictment, Mr. Milosevic and other Yugoslav leaders "planned, instigated, ordered, committed or otherwise aided and abetted in a campaign of terror and violence" directed at Kosovo Albanian civilians in 1999 and in Croatia in 1991-92. His actions resulted in the deportation of hundreds of thousands of individuals and the deaths of thousands more. He is also charged with genocide during the Bosnia-Herzegovina war.

While the world has become too well acquainted with the horrific acts that were perpetrated during those three bloody wars, proving Mr. Milosevic's complicity and responsibility is another matter. The Yugoslav leader rarely issued written orders and used close friends and associates to insulate him from direct association with the savagery on the battlefield. Apparently, the tribunal's prosecutors will try to get those confidantes to testify against Mr. Milosevic. That may yet prove difficult: Many people in the know remain loyal to the former leader -- not least because they could be incriminated by any testimony they gave. Nonetheless, he is not immune from danger: The tribunal's law provides that a superior is guilty of the acts of subordinates if he "knew or had reason to know" about crimes and he "failed to take the necessary and reasonable measures to prevent such acts or punish the perpetrators."