Over the last decade, California has led the nation in reducing its prison population. The state has shortened sentences and diverted some offenders to the counties for incarceration and supervision, transforming California’s criminal justice system into what supporters hope will become a humane model around the country. But amid the changes, crime has increased in recent years, sparking debate about the causes and giving ammunition to those leading a new effort to roll back some of the reforms. An analysis by the Marshall Project and the Los Angeles Times found that California’s crime rates remain near historic lows, but overall...