Mitigating factor
Since the end of the Nuremberg Trials after World War II, the major international courts in the world have outlawed the death penalty in their courts.  For example, in 1993, the United Nations set up an International Criminal Tribunal for the Former Yugoslavia (which is still prosecuting people as of 2016). In 1994, the United Nations Security Council set up the International Criminal Tribunal for Rwanda, to look into and punish crimes committed during the Rwandan Genocide.  Neither of these courts were allowed to hand out death sentences.