Expert system method of performing crime site analysis

• US 5,781,704 A
• Filed: 10/11/1996
• Issued: 07/14/1998
• Est. Priority Date: 10/11/1996
• Status: Expired due to Term

• Current Assignee: Environmental Criminology Research, Inc.
• Original Assignee: Environmental Criminology Research, Inc.
• Inventors: Rossmo, Darcy Kim
• Primary Examiner(s): MacDonald, Allen R.
• Assistant Examiner(s): Smith, Jeffrey S.
• Application Number:
  US08/730,465
• Time in Patent Office: 641 Days
• Field of Search: 395/10, 395/75, 705/1, 705/7
• US Class Current: 706/45
• CPC Class Codes: G06N 5/04 Inference or reasoning models
• CPC Class Codes: G06Q 99/00 Subject matter not provided for in other groups of this subclass

Abstract

An expert system method is provided that performs crime site analysis in a criminal activity area to determine a likely center of criminal activity. The method uses distances from related crime sites to determine a probability surface for the entire criminal activity area. A target area having highest values of probability becomes the center of criminal activity. The expert system can be used to access other crime databases such as witness reports to further define the criminals; residence or workplace.

Claims

1. An expert system method of analyzing crime site data for determining a base of criminal activity, comprising the steps of:

locating a plurality of related crime sites on an area map;

converting said plurality of related crime scene location data into signals representing discrete crime sites;

delineating a criminal activity area on the area map in dependence upon spacing between the plurality of crime sites;

establishing an x-y grid having a plurality of grid points within the criminal activity area;

for each grid point, determining a distance to each of the plurality of related crime sites;

for each grid point, determining a first probability value in dependence upon each distance, then combining first probability values to determine a second probability value; and

outputting a signal representing a center of criminal activity in dependence upon second probability values for the criminal activity area.

2. An expert system method as claimed in claim 1 wherein the step of generating first probability values uses a distance decay function.

3. An expert system method as claimed in claim 2 wherein the distance decay function is augmented by a buffer zone.

4. An expert system method as claimed in claim 3 wherein the step of step of generating probability values uses the following function:

##EQU3## where;

space="preserve" listing-type="equation">|x.sub.i -x.sub.c |+|y.sub.j -y.sub.c |>

B.OR left.=1

space="preserve" listing-type="equation">|x.sub.i -x.sub.c |+|y.sub.j -y.sub.c |≦

B.OR left.=0

and;

Pij is the resultant probability for point ij;

k is an empirically determined constant;

B is the radius of the buffer zone;

T is the total number of crime sites;

f is an empirically determined exponent;

g is an empirically determined exponent;

x_i, y_j are the coordinates of grid point; and

x_c, y_c are the coordinates of the cth crime site location.

5. An expert system method as claimed in claim 1 wherein the step of combining first probability values includes the step of summing first probability values together.

6. An expert system method as claimed in claim 1 wherein the step of combining first probability values includes the step of multiplying first probability values together.

7. An expert system method as claimed in claim 1 wherein the step of outputting includes the steps of generating a coded display of second probability values, overlaying the coded display on the crime activity area and correlating an area having second probability values above a predetermined threshold with a physical location to establish an area defining the center of criminal activity.

8. An expert system method as claimed in claim 7 wherein the step of outputting includes the steps of importing case data and correlating the case data with the center of criminal activity to reduce the area associated therewith.

9. An expert system method as claimed in claim 1 wherein the case data includes suspect addresses.

10. An expert system for analyzing crime site data for determining a base of criminal activity, comprising a computer having a memory for storing intermediate values, a display and a printer and a central processing unit controlled software to provide

means for locating a plurality of related crime sites on an area map presented on the display;

means for converting a plurality of related crime scene location data into signals representing discrete crime sites;

means for delineating a criminal activity area on the area map in dependence upon spacing between the plurality of crime sites;

means for establishing an x-y grid having a plurality of grid points within the criminal activity area;

for each grid point, means for determining a distance to each of the plurality of related crime sites and means for determining a first probability value in dependence upon each distance and means for combining first probability values to determine a second probability value; and

means for outputting, to the display and printer, a signal representing a center of criminal activity in dependence upon second probability values for the criminal activity area.