http://en.wikipedia.org/wiki/Sharia
Islamic law made many influences on Western legal systems.
One contribution Islamic law made to Western law, was the legal procedure. Until the Crusades, legal procedure in the West often consisted of “God’s judgments” by boiling water (or another “ordeal”) or by duel. By contrast, Islamic law decided on the basis of proof and allowed the defendants to express freely, a practice that had been established in the time of the second Caliph of Islam, Umar. Marcel Boisard argues that these procedures were transmitted to Europe via Louis IX, who instituted several reforms upon returning from the Crusades.