Anyone who doubts that race, poverty and policing drive the city’s criminal justice system might examine the case of Karina Vetrano. Vetrano, a 30-year-old white woman from Queens, was beaten to death in May 2016 in Spring Creek Park in Howard Beach. Six months later, police charged Chanel Lewis, a black man from Brooklyn, with her murder. Police say his DNA matched that found on Vetrano and on her cellphone at the crime scene and that he confessed to killing her.