Abstract: In criminal courts, prosecutors can adjust police officers' charges between arrest and sentencing -- and can therefore check unwarranted disparities in police arrests. Yet prosecutors are human and so may introduce more disparities than they offset. We use discontinuities in mandatory-prison laws to identify prosecutors' impacts on racial disparities in North Carolina state courts. We find that prosecutors' charging responses to mandatory-prison discontinuities initially compounded arrests disparities (1995-2007) but recently attenuated them (2015-2019). This reversal is concentrated in arrests typically initiated by police stops and absent from arrests typically initiated by victim reports, suggesting that prosecutors have increasingly questioned the police.