Predictive Policing Blog

Predicting Where & When Crime Will Occur Is No Simple Task

If one can accurately predict where and when crime will occur today, then law enforcement personnel can disrupt those crimes before they happen. But predicting where and when crime will occur is no simple task.

While crime may concentrate in some of the same neighborhoods year after year, the daily variation in where and when crimes occur is often large. A neighborhood may experience multiple burglaries over the course of a year, but only one or two houses in that neighborhood may be at risk today, while tomorrow it might be two different houses on the other side of the same neighborhood.

It is very difficult to predict where crime will occur in the next 10–12 hours simply based on where it occurred recently. Extensive research has shown that short-term crime patterns are driven by interactions among (1) crime generators that are built-in features of the environment; (2) repeat and near-repeat victimization that leads previous victims and their neighbors to be at a greater risk of follow-up crimes; (3) the routine activity patterns of offenders and victims that keeps risk local; and (4) substantial random noise. Each of these processes is well-known empirically, but when put together, their relationship to the emergence, spread, and disappearance of crime hotspots over time is incredibly complex.

PredPol’s methodology uses high-powered mathematics to calculate probabilities of where and when crime will occur today. The mathematics are closely related to those used to study earthquakes. Any one crime can be linked to crime generators in the environment or recent nearby crime events in the same way that an earthquake can be classified as a main shock tied to a fault in the earth or an aftershock occurring closely on the heels of a previous quake. What matters most is that the mathematics allow police to not only characterize past crime, but also use past crime to forecast with great accuracy, the locations where crime will occur in the immediate future.

The mathematics also allows police agencies to forecast crime at a very fine scale while constantly adapting to crime patterns as they change from day to day. PredPol predictions identify 500 x 500 foot boxes that are at the greatest risk of crime in the coming shift. The value of identifying such a small area is that police can zero in on a location with the greatest risk of crime today and distinguish it from nearby areas that are at significantly lower risk. Furthermore, a location that is at low risk of crime today may be at high risk tomorrow, so patrol units see different boxes on different days depending on each area’s risk level for that specific day. 

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Check out this video of PredPol's Chief Scientist and Co-Founder, Jeff Brantingham explaining the math and science behind PredPol's predictions in greater detail.

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