PARIS — The court session in The Hague was meant to be the final act of a decades-long legal process over the atrocities of the Bosnian and Croatian wars. Instead, it descended into confusion and, ultimately, death.

As judges at the International Criminal Tribunal for the Former Yugoslavia were delivering rulings on Wednesday on appeals related to Croatia’s involvement in the 1992-95 Bosnian conflict, one of the six defendants, Slobodan Praljak, who was standing, addressed the court.

“Slobodan Praljak is not a war criminal,” he declared slowly and deliberately in Croatian, just moments after judges upheld Mr. Praljak’s 20-year jail sentence for war crimes and crimes against humanity. “I reject your judgment with contempt.”

In a scene befitting the theater director Mr. Praljak had been before the Bosnian war erupted, he pulled out a small container, raised it to his lips and ostentatiously swallowed the contents. He then said, “I have taken poison.”