There are many states that have non-lawyers who act as judges in limited jurisdiction courts. So, the idea that you have to be a lawyer to be the prosecutor in those courts is problematic. But what if the prosecutor is the arresting police officer? Alexandra Natapoff has this piece in The New York Times. In part:

In hundreds of misdemeanor courts in at least 14 states, police officers can file criminal charges and handle court cases, acting as prosecutor as well as witness and negotiator. People must defend themselves against, or work out plea deals with, the same police officers who arrested them for low-level offenses like shoplifting or trespassing.

Consider South Carolina, where most of the 400 magistrate and municipal courts had no prosecuting attorneys, according to a 2017 study by the National Association of Criminal Defense Lawyers. The police prosecuted their own misdemeanor arrests, while 90 percent of defendants had no lawyers and so faced the arresting officer-prosecutor on their own. South Carolina also does not require its lower-court judges to be lawyers, so thousands of convictions occur without input from a single attorney.