The Smithsonian take a long look at New York's police force in the 1800s:
The Constitution’s Fugitive Slave Clause required northern free cities like New York to return the self-emancipated to their southern enslavers, and the NYPD and officers like Rynders were only too willing to comply, conveniently folding their hatred of black people into their reverence for the nation’s founding document. Armed with the founders’ compromise over slavery, Rynders and his fellow officers, men like Tobias Boudinot and Daniel D. Nash, terrorized New York’s black community from the 1830s up through the Civil War.
And, even worse, it often mattered little whether a black person was born free in New York or had in fact escaped bondage; the police, reinforced by judges like the notorious city recorder Richard Riker, sent the accused to southern plantations with little concern and often even less evidence.
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Part of the fear emanated from the fact that Rynders’ confederates Boudinot and Nash did not wear uniforms or carry any kind of badge signifying their authority. The familiar dark blue uniforms of the NYPD were not instituted until the 1850s, so African Americans harassed or arrested by the police could not even be sure that they were being accosted by legal authorities.
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for months, the city actually had two competing police departments who battled each other as much as they combatted crime.