LEIDSCHENDAM, the Netherlands — Charles G. Taylor, the former president of Liberia and a once-powerful warlord, was sentenced on Wednesday to 50 years in prison for his role in atrocities committed in Sierra Leone during its civil war in the 1990s.

In what was viewed as a watershed case for modern human rights law, Mr. Taylor was the first former head of state convicted by an international tribunal since the Nuremberg trials in Germany after World War II.

Mr. Taylor was found guilty of “aiding and abetting, as well as planning, some of the most heinous and brutal crimes recorded in human history,” said Richard Lussick, the judge who presided over the sentencing here in an international criminal court near The Hague. He said the lengthy prison term underscored Mr. Taylor’s position as a government’s leader during the time the crimes were committed....