Definitions of “genocide" and “crimes against humanity" come down to mass murder of a specific group of people versus the slaughter of individuals on a massive scale. University College London law professor Philippe Sands identifies the father of each perspective: Rafael Lemkin coined the word “genocide" and Hersch Lauterpacht codified “crimes against humanity." Both men were consultants at the Nuremberg Trials; both were Jews from Lvov, a formerly multicultural city in Poland where Sands’ ancestors also lived. East West Street is a compelling investigation of a chain of connections and coincidences linking the author’s family with Lemkin and Lauterpacht as well as their Nazi foes. Lemkin and Lauterpacht disagreed over their understanding of international law. At Nuremberg, the judges sided with Lauterpacht in condemning crimes against humanity while remaining silent on genocide.