At its simplest geographic profiling involves sticking pins in a map and drawing conclusions therefrom. However these days it most commonly refers to a sophisticated probability based methodology normally deployed in criminal investigations that provides a means of deducing the likely whereabouts of the perpetrator of a series of linked criminal offences. Or as one exponent put it, it is a way of turning "our radar into these sea of crimes to see where offenders are most likely to be lurking".

The origins and development of geographic profiling

The first known use of geographic profiling as an investigative tool was in the mid nineteenth century when it was employed by a certain Dr John Snow. Faced with a cholera epidemic at Soho in London during the year 1854 he took a map of the area on which he marked the number of victims in each property. Then, acting on the theory that the disease was caused by a contaminated water source, Dr Snow also marked the location of all the local water sources on his map. By comparing the incidence of the disease to the location of the water sources, he concluded that a water pump at the corner of Broad Street and Cambridge Street was at the epicentre of the epidemic, went there and removed the pump handle and so abruptly terminated the epidemic.

However it was not until over a century later that it was first used as a tool in a criminal investigation by one Stuart Kind when he was called in to assist the Yorkshire Ripper inquiry on the 1st December 1980. Since at that time the police had no idea of who they were looking for, Kind decided to map out the attacks attributed to the Yorkshire Ripper. Then, working on the assumptions that the killer would want to return home as soon as possible after an attack, and also that the closer he was to home, the later he would carry out an attack, he proceeded to calculate where home might be for the Yorkshire Ripper. On the 10th December 1980 Kind delivered a short monograph which predicted that the perpetrator lived in the Mannigham/Shipley area of Bradford. As things turned out the police never had the time to act on this conclusion, as by complete chance a certain Peter Sutcliffe was arrested by Sergeant Robert Ring on the 2nd January 1981 and turned out to be the very man they were looking for. However since Sutcliffe lived in Heton, which was halfway between Mannigham and Shipley, the validity of Kind's conclusion was thereby demonstrated.

Whilst it has also been claimed that the Los Angeles Police Department used something akin to geographic profiling in their hunt for the Hillside Strangler in 1977 one suspects that have been many cases, dating back to the very dawn of policing, where detectives have frequently mapped out the incidence of linked crimes, and made an intelligent guess as to the likely whereabouts of the perpetrator. What was however different about Stuart Kind's approach was that he didn't use his judgement to reach his conclusion, he used mathematics. Unfortunately his breakthrough went largely unnoticed, since although Kind did indeed publish the details of his methodology and results in the Journal of Navigation in 1987 and in a book The Scientific Investigation of Crime which also appeared in 1987, neither received much attention, and his work was largely ignored and forgotten.

Some years later David Canter, from the Investigative Psychology Department at the University of Liverpool, was called in to assist the police in their investigation of the so-called Railway Rapist or North London Rapist in 1985. Canter wasn't aware of Kind's work at the time, and so re-invented a very similar methodology which ultimately assisted the police in their apprehension of John Duffy for the crimes in question. Canter subsequently employed a computer programmer named Malcolm Huntley, who used formulae derived from Newton's theory of gravity to develop an algorithm which was used as the basis of a program named Dragnet. The algorithm was tested out on data from seventy US serial killers and later used for the identification and arrest of John Thompson, the Auckland Rapist in New Zealand on the 15th July 1995, whilst the Las Vegas Metropolitan Police Department also used Dragnet in their identification and arrest of Justin 'Jug' Porter on charges of murder and six counts of rape.

As far as David Canter was concerned Dragnet was based on principles that were "obviously part of an existing set of ideas" and so he never considered the possibility that "this might be a process that could be given a catchy name and turned into a commercial product". Indeed as an academic he allowed fellow academics free use of Dragnet, whilst everyone else was simply charged a "small handling fee". However whilst Canter was developing Dragnet, a detective inspector in Vancouver named Kim Rossmo, who was entirely unaware of either his work or that of Stuart Kind, was also working within this 'existing set of ideas' and used a similar methodology whilst he was working at the Vancouver Police Department in 1990. Rossmo developed his own algorithm which he named as Criminal Geographic Targeting in 1991, which was later incorporated into the Rigel program, launched in 1996, a year after he'd completed his doctoral dissertation at Simon Frasier University's School of Criminology on the very subject of geographic profiling.

It was therefore Kim Rossmo who came up with the "catchy name" of 'geographic profiling' and turned it into a commercial product and it is therefore Rossmo who is often mistakenly credited as the originator of the methodology. Indeed there was one geographer at Louisiana State University by the name of Milton Newton who did indeed read Stuart Kind's work and wrote his own simple profiling program in visual basic back in 1985 to add to the list of those who had developed the technique well before Rossmo had ever considered the idea.

However what all this does mean is that in practice geographic profiling comes down to a number of competing commercial computer programs such as CrimeStat, Dragnet and Rigel where naturally each vendor claims that their product is superior to the competition. For example Maurice Godwin, who is president of Godwin Trial and Forensic Consultancy, which developed the Predator geographical profiling system, has been publicly critical of the geographical profile developed by Kim Rossmo on the I-95 sniper shootings which he claimed was just plain wrong, as opposed to his own 'geoprofile' based on his wedge theory which accurately predicted the most likely "home base area" for the killers.

The nature of geographic profiling

What geographic profiling does not do is identify precisely who has committed any particular crime; all it does is identify that the perpetrator is likely operating from a particular limited geographical area. It is probably best seen as a method of filtering the large amounts of data that the police typically gather during any large scale inquiry, where the value of its conclusions lie in the fact that they can be linked to other information, such as vague descriptions of what vehicle the likely suspect is driving, or data on existing criminal convictions, which can enable the police to focus their attention on a comparatively small number of potential suspects. It is, of course, most widely used in the investigation of suspected serial killings, but the methodology can be similarly applied to any series of crimes such as various sexual offences or indeed burglaries.

Conceptually speaking geographic profiling is based on what is known as the "least effort principle", which is to say, the idea that individuals will take the easiest opportunity available, and that they will therefore travel no further than necessary to commit their desired crime, subject to maintaining a 'buffer zone' around their 'anchor point' or 'base of operations', which is generally speaking their actual home, although it might alternatively be their place of work, or something as basic as a motorway junction. However although geographic profiling has chalked up a number of successes and proved its value as an investigative tool, it is not quite as powerful a weapon as it might seem, as there are a number of assumptions which generally underlie the methodology which tend to limit its practical value.

The most important assumptions made are;

(1) That the offender is "using an appropriate hunting method", which is to say that he or she is a 'local hunter' and not a 'poacher' or 'commuter'. Or to put it another way, it is assumed that the offender actually has a base within the area defined by the crimes committed, an assumption also known as the circle hypothesis. Where the perpetrator is actually coming in to the area to commit crimes from elsewhere then geographic profiling is unable to provide a sensible answer.

(2) That there is indeed a series of crimes that have been committed by the same offender (Rossmo has claimed the minimum is five). As it turns out, it is not that easy to be sure that any series of crimes really are the work of the same person without hard forensic evidence linking crimes together. (And where hard forensic evidence does exist it is likely to have led to the detection and apprehension of the perpetrator without the use of geographic profiling in the first place.) As far as serial killers are concerned this generally involves identifying the killer's 'signature', which leads us into an entirely different argument, since there are those that contend that the idea that a serial killer leaves a signature is something borrowed from fiction and has no counterpart in the real world.

(3) That the series of linked crimes are relatively complete and that any missing crimes should not be "spatially biased". This can be a particular problem in certain countries such as the United States, where there are adjacent and overlapping police jurisdictions that often don't talk to one another.

(4) That the perpetrator has a "single stable anchor point over the time period of the crimes". Which is to say that they haven't moved home recently, or otherwise changed their base of operations.

(5) That the "target backcloth is reasonably uniform". That is, the same kind of people are the victims of the crimes in question, since fairly obviously different patterns of behaviour are likely to be adopted by offenders depending on what kind of people they are targeting.

Clearly therefore the advice to any would be serial killer would be to move home regularly, vary your targets as much as possible, travel as far as possible to find them, adopt a number of different and identifiable signatures and switch between them regularly and, if you happen to operating in the United States ensure that you commit your crimes in as many separate jurisdictions as possible. Whilst such remarks might appear facetious, it is worth remembering that criminals can read or at least watch television (witness the CSI effect) and they will therefore change their behaviour in the light of what actions the authorities take to identify and aprehend them.


SOURCES

  • David Canter, Criminal Shadows: Inside the Mind of the Serial Killer (Harper Collins, 1995)
  • Kim Rossmo, Ian Laverty, Brad Moore, Geographic Profiling for Serial Crime Investigation
    from Geographic Information Systems and Crime Analysis edited by Fahui Wang (IGI Publishing, 2005)
  • Katherine Ramsl, Geographical Profiling, from The Crime Library
    www.crimelibrary.com/forensics/geog/
  • Kim Rossmo, An Evaluation of NIJ's Evaluation Methodology for Geographic Profiling Software, March 9, 2005
    http://www.txstate.edu/gii/documents/Response%20to%20NIJ%20GP%20Evaluation%20Methodology.doc
  • Ned Levine, The Evaluation of Geographic Profiling Software:Response to Kim Rossmo's Critique of the NIJ Methodology May 8, 2005
    http://www.nedlevine.com/Response%20to%20Kim%20Rossmo%20Critique%20of%20the%20GP%20Evaluation%20Methodology.May%208%202005.doc.
  • Geographic Profiling
    http://www.txstate.edu/gii/geographicprofiling.html
  • Accurate Psycho-Geographical Profile
    www.investigativepsych.com/snipergeoprofile.htm
  • A review of David Canter's Mapping Murder: The Secrets of Geographical Profiling by Maurice Godwin
    http://www.amazon.co.uk/review/R2G7L945HZTZS7?ASIN=1852270780

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