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Seeking safe haven. Ethnic Albanian refugees flee their home city, Pec, and take a road leading to the Kosovo-Montenegro border in March 1999.

Patterns of Refugee Flight

THE HAGUE, NETHERLANDS--The war crimes trial of Slobodan Milosevic, Yugoslavia's former president, shifted into a new phase yesterday when the court heard from the sole scientific expert expected to be called by the prosecution. Patrick Ball, deputy director of the science and human rights division of the American Association for the Advancement of Science (AAAS), ScienceNOW's publisher, testified that his team's statistical evidence is consistent with the hypothesis that Yugoslav forces conducted a systematic campaign of killings and expulsions of Kosovar Albanians in spring 1999.

The prosecution led Ball through key sections of a technical report he co-authored, tracing its elements for judges in the International Criminal Tribunal for the Former Yugoslavia (ICTY). The report, prepared by AAAS and the American Bar Association's Central and East European Law Initiative, relied on three main data sources: records from Albanian border guards who had logged more than 400,000 people fleeing Kosovo that spring; interviews with Kosovar Albanians; and records of ICTY-ordered exhumations.

After identifying peaks of refugee movement and killings in late March, mid-April, and early May 1999, Ball and his colleagues examined three potential causes: Kosovo Liberation Army (KLA) activity, NATO's bombing campaign, and a systematic campaign by Yugoslav forces. "We made every attempt to be as conservative as possible" in estimating the number of victims, Ball said, "to present a statistical case as favorable as possible to the hypotheses that we ultimately rejected." KLA activity as reported in the Serb press, they found, rarely occurred in Kosovo municipalities at times that could be linked to killings and refugee movements. And NATO bombs began falling only after the first wave of migration and killings.

Yugoslav army activity, on the other hand, ebbed and flowed roughly in sync with the refugee movements and killings. "We found a consistent and drastic decline both in refugee movement and people killed," Ball stated. The statistical evidence, he concluded, "is consistent with the hypothesis that Yugoslav forces were the cause."

Milosevic, who has refused to recognize the tribunal's legitimacy and is representing himself in the trial, suggested during cross-examination today that the data from the Albanian border guards could have been fabricated. He also argued that the three hypotheses examined in the report oversimplified the Kosovo conflict, which he called "an extremely complex phenomenon." Ball acknowledged that his group's statistical approach "does not exclude the possibility that there may be other causes," but he stood by the conclusions.

The trial, which is examining alleged war crimes in Kosovo, Bosnia-Herzegovina, and Croatia, is expected to last until early 2004.