AMSTERDAM (AP) -- One of Ratko Mladic's most senior commanders was in no doubt who was ultimately responsible for the massacre of 8,000 Muslims in the Bosnian enclave of Srebrenica in July of 1995.

"This chain of command originated with Mladic," argued Radislav Krstic, the corps commander of the forces that controlled this part of eastern Bosnia, where the slaughter unfolded.

Through much of the 16 years Mladic was in hiding, evidence has been accumulating in the case files of the Yugoslav war crimes tribunal of his key role in genocidal crimes in Bosnia, as one after another of his subordinates were sent to prison.

In one sense, Mladic has already been tried by proxy. His name figures large in the testimony and documents at the trials of Bosnian Serb army officers, including Krstic and three others who have been convicted of genocide-related charges for the mass killings in eastern Bosnia.

The slaughter in Srebrenica was of such a scale that tribunal judges drop legal niceties in describing it. As one verdict put it, the weeklong bloodbath were crimes "committed with a level of brutality and depravity not previously seen in Yugoslavia ... and are among the darkest days in modern European history."

The judgment in Krstic's 2004 appeal upheld the lower court's finding that "Mladic directed the operation." The defense and prosecution "agreed that General Mladic was the main figure behind the killings."

Mladic and his political boss, Radovan Karadzic, repeatedly emerge as the two central figures in the conduct of the 1992-95 Bosnian war, leading the meetings at which military strategy was decided and giving the orders to carry out their ambition of "cleansing" areas of non-Serbs.

Judging from the Krstic case and other trials, the evidence against Mladic, the overall Bosnian Serb army commander, appears overwhelming. But legal experts said it must be put to the test against Mladic's defense team, and they cautioned against inferring guilt from the convictions of his subordinates.

At question for the court to decide is whether Mladic was ultimately responsible, directly or indirectly, for the deliberate massacre at the U.N.-declared safe zone.

Srebrenica is the most serious incident of the war for which he stands accused. The lengthy list of charges also includes ordering the four-year-long siege of Sarajevo. In all, about 100,000 people were killed in the war.

In Belgrade, Mladic's lawyer said Monday he would appeal the order to extradite the 69-year-old former general to the tribunal in The Hague on the grounds of ill health.

Mladic's son Darko said Sunday his father was not responsible for Srebrenica massacre and that he gave no orders for the killings.

"Whatever was done behind his back, he has nothing to do with that," Darko Mladic told reporters in Belgrade, where the former general was taken following his capture last week.

Even if proven true, Mladic could be held to account for war crimes. Earlier cases have established a principle of "command responsibility," holding that commanders are liable if they failed to prevent or punish illegal actions of their men.

"You don't necessarily have to give direct orders," said Alison Smith, the legal Counsel for the Belgian-based group No Peace Without Justice.

All together, 12 Bosnian Serbs, many of them senior officers, have been convicted of genocide, war crimes or crimes against humanity for Srebrenica. Besides the Karadzic case, another four trials of military men related to the massacre have yet to be completed.

"The evidence strongly suggest that the criminal activity was being directed by some members of (Bosnian Serb army) Main Staff under the direction of Gen. Mladic," said the Krstic appeal.

The International Criminal Tribunal for the former Yugoslavia was created in 1993 -- even before the Balkan wars reached their climax. The vast majority of the 161 people it indicted were Serbs, a fact that has prompted many Serbs to denounce the U.N. court as biased.

Mladic and Karadzic were indicted after Srebrenica and both went into hiding. Karadzic was captured in 2008 and his trial is still in the early stages.

In 2001, Krstic became the first person convicted of genocide in Europe -- a crime that was defined only after the Holocaust in World War II. An appeals judgment three years later reduced the charge to complicity in genocide and set the sentence at 35 years imprisonment.

Equally important as the individual case was the ruling that genocide -- the intent to destroy an ethnic or religious group in whole or in part -- had occurred in Srebrenica. That finding, reaffirmed in other tribunal cases, also was upheld by the U.N.'s highest judicial body, the International Court of Justice.

Last year, two other high ranking security officers, Vujadin Popovic and Ljubisa Beara, were handed genocide convictions for Srebrenica and received the maximum punishment of life imprisonment, while a third was convicted of complicity in genocide. Their appeals are pending.

The difficult task for prosecutors, as in all genocide cases, is to prove Mladic's prior intention to eliminate the Muslims from the enclave by any means.

"Somebody had to have that intent. That's why the Karadzic trial is so interesting," said Geraldine Mattioli of Human Rights Watch. "And that's why the Mladic case will be interesting."

The third man at the pinnacle of the command structure was former Yugoslav President Slobodan Milosevic. The three were accused of plotting together to drive non-Serbs from areas of Bosnia to carve a Greater Serbia from the ruins of Yugoslavia.

Milosevic died in 2006 as his four-year-long trial in The Hague was nearing an end.