The proof standard for an arrest on a complaint is probable cause that a crime has been committed. Probable cause is also the standard for indictment, but there’s an important difference. Complaints often get dismissed; indictment is that beginning of the formal process that leads to trial and a determination of guilt. Prosecutors thus do not indict unless they believe a rational jury could find guilt beyond a reasonable doubt, a standard more demanding than probable cause. In the typical street-crime case, then, a person is arrested on a complaint and either detained or granted bail. Within a certain statutory...