Crime Mapping & Geographic Profiling - Technology and Communications -

Crime Mapping & Geographic Profiling



Tim Dees | From the December 2008 Issue Monday, December 22, 2008

There's a kind of voodoo associated with geographic profiling. An analyst pours all sorts of seemingly random data into their computer and produces a pretty map with color-coded mountains where no mountains exist. They tell you you'll find your bad guy on the tops of the highest mountains. It's not all that far off from looking for water with a divining rod, but it works.

There was geographic profiling before there were computers to do it. A long time ago, I was testifying at the trial of a man I arrested for drunk driving. He had been stopped on a street that was home to a dozen small working-class bars, a target-rich environment for me when I was working deuces. I could spend my uncommitted time driving up and down the two miles or so where the bars were, and it wouldn't be long before I found myself behind a driver who was weaving, speeding, driving 15 miles per hour or exhibiting some other behavior that led to the two of us having a chat.

Defense counsel was trying to get me to say I stopped every car I saw on that street, reasonable suspicion or otherwise. I hadn't done that, and refused to say I had. He was getting quite frustrated, having asked essentially the same question nine different ways. He finally got to a question I could answer: "Why did you spend so much time driving up and down Wells Avenue?"

"When you go duck hunting," I said, "you have to be where the ducks are. They won't line up on your front porch and wait to get shot."

Geographic profiling tells you where the ducks are.

The Electronic Pin Map
Another remnant of policing's Bronze Age are pin maps. Pin maps were posted in the squad room and maintained by someone who didn't like to go outside. Colored map pins would be placed on the map where burglaries, robberies, auto thefts and other reported crimes had occurred. Diligent patrol officers were supposed to check the pin maps for their beat and give greater attention to the areas where the pins were accumulating. More commonly, officers would just wait until the room was empty and then move some pins to someone else's beat, thus making themselves appear to be doing a sterling job of crime fighting.

Geographic information systems (GIS) have given us a kind of electronic pin map, with data linked to each point identified on the map. We see these maps used all the time, for all sorts of applications that have little to do with crime. Bring up Google Maps in your web browser and enter "pizza" followed by your zip code. You'll be presented with a map with a "pin" stuck in at the location of every pizza joint in town. Zoom in and click on a pin, and the address, phone number and maybe even a review of the pizza will pop up.

Crime maps do the same thing, with each pin linked to a crime report or other occurrence of interest to the police. The beauty of the electronic map is that it can be layered with an infinite number of plots of other data, such as the location of schools, sex offender residences, bus routes, methadone clinics or anything else that may cause an analyst to see a pattern where none was previously apparent.

Local government GIS systems, which are now commonplace, maintain precise plots of everything from the location of fire hydrants to properties where business licenses have been issued. Global positioning system (GPS) hardware has made the placement of these landmarks highly accurate without the need to use land surveyors to deliver the same data. Several devices are available that will record a digital image from hundreds of yards away, at the same time logging the latitude, longitude and elevation of the point in the crosshairs with precision of about four inches.

Geographic Profiling
Crime mapping is just the start of geographic profiling. Criminal profiling is usually seen as a last resort for investigators when they have too few leads and too many potential suspects. The typical scenario involves the case officer compiling a summary of the crime or crimes for analysis by the Behavioral Science Unit at the FBI's Quantico facility. The analysts there study the available data and possibly dance around a fire while sacrificing small animals, and come up with a description of the person they believe is responsible. They have an excellent track record with this, although a profile may be only 60 80 percent accurate, and until the bad guy is identified, no one knows which 60 80 percent applies. But the profile may allow investigators to de-prioritize suspects who are outside of the profile and concentrate on those who are the best fit.

Geographic profiling works similarly, using complex algorithms to predict where a suspect might live, work or frequent. The foundation of the data is usually the crime map of the locations where linked incidents have taken place. Most criminals have a style or preference for their work. A burglar might use the same method of entry and search, or prefer targets with specific attributes, such as proximity to freeways or money stored in a floor safe. Serial rapists and murderers may prefer a certain age, gender, race or occupation, and use a similar weapon or restraining method in their crimes. Analysis of these factors will produce the sample of incidents most likely committed by a single person.

Other factors entered into a geographic profile may include transportation routes and time-and-distance calculations. A suspect with access to a motor vehicle has a greater choice of routes than one who gets around on a bicycle or by public transportation. The economic and ethnic makeup of neighborhoods can create a crook-friendly environment or serve as a barrier or obstacle to be avoided. A rapist with a broken-down van will attract attention in an upscale neighborhood, and a white crook will avoid black neighborhoods for the same reason.

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Tim DeesTim Dees was a law enforcement officer for 15 years in Nevada, and taught criminal justice full time for eight years. He holds a bachelor's degree in biological science, a master of science degree in criminal justice, and the Certified Protection Professional credential from ASIS International.


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