This policing innovation helped fight crime. But it also led to more corruption.

One of the big successes in US policing over the past three decades was the push to make law enforcement more data-driven. The big crime-tracking system that came out of this, CompStat, has been widely credited with helping cut crime in the US.

But what if this approach has also led police to be too focused on data, turning policing into a numbers game in which cops try to make as many arrests as possible and manipulate the figures to look good?

John Eterno, a retired New York City Police...