A pandemic experiment in criminal justice reform takes hold in one of America's most violent cities.A year ago, as the coronavirus began to spread across Maryland, Baltimore State’s Attorney Marilyn Mosby stopped prosecuting drug possession, prostitution, minor traffic violations and other low-level offenses, a move aimed at curbing Covid-19's spread behind bars.That shift — repeated by prosecutors in many other cities — didn’t just reduce jail populations. In Baltimore, nearly all categories of crime have since declined, confirming to Mosby what she and criminal justice experts have argued for years: Crackdowns on quality-of-life crimes are not necessary for stopping more...