More than Just Lines on a Map: Best Practices for U.S Bike Routes
Fundamentalsof Crime Mapping 4
2. Mental Maps
◦ Over time, making repetitive journeys to various
locations gives us knowledge of the routes and
characteristics of these places
Activity space
◦ The well-known areas, those places visited
frequently and the routes that connect these areas
Awareness space
◦ There are also locations that, while we do not
regularly frequent them, we still know about them
Target backcloth
◦ The distribution of targets in the environment
3. Journey an offender travels when he commits
a crime
Generally measured as the distance between
the offender’s home and the location of his
crime AV E R AG E O F
CR I M E C AT E GO R Y T R IPS M E D IA N* M O DE **
A GG . AS S AU L T 1 . 18 1. 4 9 0. 2 0
AR S O N 1 . 32 0. 5 3 0. 5 9
AU TO T H E F T 2 . 88 2. 4 0 1. 8 5
BU R GL A RY 2 . 34 1. 1 0 2. 7 5
D R UG O F F E N S E S 2 . 27 1. 5 3 8. 4 1
M UR D E R 2 . 38 1. 7 5 1 0. 9 5
R AP E 1 . 35 1. 7 0 N/ A
RO B BE RY 3 . 23 1. 9 5 2. 8 3
T H EF T 3 . 18 1. 8 6 0. 5 3
* & ** C alcu late d on n on -z er o d ista nc es on ly
4. Crimes against persons, such as
homicide, assault, and rape, occur closer to
home than property crimes, such as larceny
and burglary (Brantingham &
Brantingham, 1981).
Overall average about 2 miles
Distance decay
◦ Probability decays or drops off as distance from the
offender’s residence increases
5. Burgled
Homes
X
X X
X
X
Suspect’s
X
Home and Buffer Zone
X
6. It is important to note that offenders do
commit crimes within their buffer zone;
however, there may be areas outside their
buffer zone where they commit more crimes.
The buffer zone represents an area of reduced
activity not an area of “no” criminal activity
7. Police investigation strategy that uses the
locations in a connected crime series to narrow
the search for likely suspects
Manage large amounts of information
Help focus limited resources on the most likely
area of offender residence
Crime series
◦ a set of crimes believed to have been committed by
the same offender.
8. Searching methods
◦ Hunter (or marauder)
sets out from his home specifically to find a victim
◦ Poacher (or commuter)
specifically sets out to find a victim, but his search is
from a location other than his home
◦ Troller
opportunistically encounter a victim during normal
activities
◦ Trapper
set up a situation in which victims come to them
9. Methods of attack
◦ Raptor
attacks the victim upon encounter
◦ Stalker
follows the victim away from the encounter point then
attacks
◦ Ambusher
attacks a victim that he has lured to a location he
controls
10. Investigative Strategies
◦ Prioritizing records from the various computerized
police files
◦ Prioritize areas for directed police patrols or area
canvasses
◦ Direct community mailings and/or conduct a media
campaign
11. Software Available
◦ RIGEL
Developed by Environmental Criminology Research Inc. (ECRI)
of Vancouver, British Columbia, Canada, uses the Criminal
Geographic Targeting algorithm invented by Dr. Kim Rossmo
in 1991 to produce a probability map
◦ Dragnet
created by Dr. David Canter of the University of
Liverpool, England, uses a negative exponential mathematical
function to produce a probability map
Crime Analysis Unit Developer Kit free
◦ Crime Stat III (JTC only)
created by Ned Levine and & Associates of Houston, Texas
Free through NIJ