**Rossmo's formula** is a geographic profiling formula to predict where a serial criminal lives. The formula was developed and patented by criminologist Kim Rossmo and integrated into a specialized crime analysis software product called Rigel. The Rigel product is developed by the software company Environmental Criminology Research Inc. (ECRI), which Rossmo co-founded.

## Contents

## Formula

Imagine a map with an overlaying grid of little squares named sectors. If this map is a raster image file on a computer, these sectors are pixels. A sector
*i* and column *j*, located at coordinates (*X _{i}*,

*Y*). The following function gives the probability

_{j}where:

Here the summation is over past crimes located at coordinates (*x _{n}*,

*y*).

_{n}*p*to switch between the two terms. If a crime occurs within the buffer zone, then

*n*-th crime site

## Explanation

The summation in the formula consists of two terms. The first term describes the idea of *decreasing probability with increasing distance*. The second term deals with the concept of a *buffer zone*. The variable

The main idea of the formula is that the probability of crimes first increases as one moves through the buffer zone away from the *hotzone*, but decreases afterwards. The variable

The distance is calculated with the Manhattan distance formula.

## Applications

The formula has been applied to fields other than forensics. Because of the buffer zone idea, the formula works well for studies concerning predatory animals such as white sharks.

This formula and math behind it were used in crime detecting in the Pilot episode of the TV series *Numb3rs* and in the 100th episode of the same show, called "Disturbed".