The drug war that has turned Ju?rez, Mexico, into a killing field that has claimed more than 7,000 lives since 2008 captures headlines almost daily. But few accounts go all the way down to the streets to investigate the lives of individual drug users. One of those users, Scott Comar, survived years of heroin addiction and failed attempts at detox and finally cleaned up in 2003. Now a graduate student at the University of Texas at El Paso in the...