John Demjanjuk's Nazi war crimes trial resumes today in Jerusalem after breaking off two months ago when one of the three trial judges suffered a heart attack. The judge, Zvi Tal, has recovered. Demjanjuk, a Ukrainian-born retired auto worker from Cleveland, is charged with operating gas chambers at the Treblinka death camp in Nazi-occupied Poland in World War II. Five survivors have identified him as the brutal guard nicknamed "Ivan the Terrible." Demjanjuk claims that he is a victim of mistaken identity.