By Tina Rosenberg, Foreign Policy, March/April 2012 issue

The choreography of a typical human rights investigation goes like this: Researchers interview victims and witnesses and write their report. The local media cover it -- if they can. Then those accused dismiss it; you have nothing more than stories, it's one word against another, the sources are biased, the evidence faked. And it goes away.

On March 13, 2002, in a courtroom in The Hague, something different happened. In the trial of Slobodan Milosevic, Patrick Ball, an American statistician, presented numbers to support the case that Milosevic had pursued a deliberate policy of ethnic cleansing [....]

Traditionally, human rights work has been more akin to investigative reporting, but Ball is the most influential of a handful of people around the world who see that world not in terms of words, but of figures. His specialty is applying quantitative analysis to mountains of anecdotes, finding the correlations that coax out a story that cannot easily be dismissed.

Could the movements of refugees have been random? No, Ball said. He had also plotted killings of Kosovars and found that both phenomena occurred at the same times and in the same places -- flight and death, hand in hand. "I remember well the moment of astonishment that I felt when I saw the killing graph for the first time," Ball replied to Milosevic. "I assumed I had made an error, because the correlation was so close."

Something had caused both phenomena, and Ball examined three possibilities [....]

In testifying, Ball was doing something other human rights workers can only fantasize about: He confronted the accused, presented him with evidence, and watched him being held to account [....]