It was an unspeakable nightmare. As Andre Daniels was held at gunpoint outside his San Francisco housing project apartment early one morning three years ago, his wife was sexually assaulted inside their home while their two children slept. Daniels, then 31, was determined to seek justice for his family. So he did what is often considered unthinkable in a community hostile to "snitching." He helped the police. Then he made another fateful decision: He spurned the burdens of the city's witness protection and relocation program. He figured he would simply move his family to safety a few miles away to...