"Predictions are tricky, especially if they are about the future." The source of that quote is unknown, but its truth is obvious.
There's a pretty good definition of Predictive Policing at this article from last year: Is Predictive Policing the Law-Enforcement Tactic of the Future?. To wit:
Known as predictive policing, the practice involves analyzing data on the time, location and nature of past crimes, along with things such as geography and the weather, to gain insight into where and when future crime is most likely to occur and try to deter it before it happens.
When police departments try to predict crime they are successful, up to a point. The mapping of crime hot spots has been around for quite a while. And police departments have used it successfully to highlight areas where more patrols might be useful.
It has been well known for years that a small number of people commit most of the crimes. Those individuals become well known to police. (The issues of race and privacy permeate the atmosphere inhabited by police and citizens, but that's a topic for another day.) The issue of what to do to actually reduce crime is an ongoing problem.
Furthermore, new influences are emerging. Shibani Mahtani updates us on a recent development in Social Media Emerges as New Frontier in Fight Against Violent Crime. (It's behind a paywall but available here for free.) There we learn that police are grappling with the influence of social media on prospective murderers. It's not a good influence. Here's an excerpt:
Facebook and other platforms have emerged as new frontiers in the fight against violent crime that continues to grip major cities.
In Chicago, which is on track to have more than 600 murders for the second year in a row, a number it had been below for over a decade prior, community leaders and police say the immediacy of these platforms has played a major role in escalating disputes, while also providing more evidence that can aid arrests and convictions.
“It pours an accelerant on what was already there,” said Eric Sussman, the first assistant state’s attorney for Chicago’s Cook County.
The Chicago Police Department and prosecutors don’t keep data on how many instances of violence were provoked by an exchange on social media, but they say anecdotally that they are seeing a rise in the number of “petty conflicts that have leapt from social media platforms to violent crimes on the street.” A Wall Street Journal tally found at least 100 cases nationally where an act of violence was streamed on just one of these platforms, Facebook Live, since it was launched in early 2016.
“Unfortunately, in too many instances, these conflicts are resolved with a gun,” said a Chicago police spokesman.
Unfortunately, like so many law enforcement innovations, use of Facebook posts is more helpful in clearing crimes than actually preventing them. There are some who might suggest custom notification with warnings to people who pop up on the list of potential criminals. But if there is a disproportionate number of minorities in that group then it becomes problematic.
In any event, that quote at the top of this post still stands. Predictions are tricky, especially if they are about the future.