10.3.3.2 Reliability

up prostitutes, parked a short distance away, and then killed and dumped their bodies. While not identical, the encounter and body dump sites in this series are close to being equivalent. The Hillside Stranglers, by contrast, originated their victim disposal trips from Buono’s home where the murders took place. The second problem occurs when combined crime locations produce a hunting area larger than that found with a single site type, resulting in the possibility of a greater search area, even though the hit score percentage is smaller. This problem is most likely to occur if the two crime site areas are incongruent. Clifford Olson appeared to use different mental maps for his victim searches and body dumps. Aileen Wuornos dumped victim’s bodies and abandoned their vehicles at different sites, the former suggestive of where she was coming from, and the latter of where she was going to.

•Preference should be given to the crime site type that affords the greatest degree of choice to the offender. Site types with constrained target backcloths tell us little about the criminal. If victim specificity leads to spatial bias then encounter locations may not be the best profiling option. Similarly, body dump sites in isolated areas may reveal only general detail about an urban killer.

The limitations of the CGT model are set by the hunting typology. Because the process assumes the offender’s anchor point lies within the hunting area, it cannot determine the residence of poaching offenders who commute. Experience has shown, however, that often some form of secondary anchor point draws a poacher into the crime area — a workplace, former residence, or the home of a friend or relative. The results of the geoprofile then point to the secondary site, and to the degree the offender can be associated with this location, investigators will find the geographic profile of value.

10.3.3.3 Utility

No matter how valid or reliable a particular technique, it will have little value if it cannot be used within the practical context of a police investigation (Baeza, 1999). Even a highly accurate CGT prediction (i.e., a small hit score percentage) will not lead police investigators to an offender’s door. Certain psychics have allegedly been successful in finding criminal offenders,66 missing people, and buried bodies (Lyons & Truzzi, 1991; but see Kocsis et al., 1999). Geographic profiling cannot do this. The process is an information management system, and to that end it must be compatible with the overall police investigation.

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Table 10.3 Urban Population Density

The scope of the search area for a given CGT hit score percentage depends upon the size of the hunting area. With a small hunting area the geoprofile can outline the streets or blocks where the offender most probably resides; with a large hunting area it will indicate the cities or towns. The resolution of an analysis is bounded by its information input. Investigative strategies based on a geographic profile must consider both expected hit score percentage and search area size. Some tactics possible at the local level are not feasible on a larger scale.

Table 10.3 lists average population and household estimates for five urban area types in Vancouver, British Columbia (1991 Canada Census data; Vancouver local areas 1981–1991, 1994). Figures are provided for metropolitan district, core city, and high, medium, and low density residential neighbourhoods (these estimates are somewhat high in that many areas contain uninhabited regions such as industrial sectors, parks, water, farmland, or wilderness). While numbers vary by city and region, it can be seen that even a search area as small as one square kilometre contains hundreds of people. This suggests there may be limited investigative value in a map that only delineates the most probable area of offender residence. In other words, geographic profiling does not result in an “x” that marks the spot; instead, it provides an optimal search strategy. It is therefore important that the profile be properly integrated with the overall investigation.

The Paperbag Rapist was responsible for at least 79 attacks in Greater Vancouver from 1977 to 1985 (Alston, 1994; Eastham, 1989). These covered an area of 1873 square kilometres (723 mi2). After John Horace Oughton was identified as a suspect, an undercover policewoman gained access to his apartment and observed a pin map on the wall showing the locations of his crimes. He was being careful not to follow a pattern. Despite efforts to avoid this, Oughton still left behind a “fingerprint” of his mental map; in a retro-

66 Moscow police have allegedly used a pair of psychics with the ability to sense “death’s geography” to help them locate bodies. But a Russian clairvoyant contacted during the Chikatilo murder investigation incorrectly told police there were two offenders, who lived high up a mountain (Lourie, 1993). A British medium claims to have accurately predicted the Yorkshire Ripper’s name and street address 18 months prior to the arrest of Peter Sutcliffe (Lyons & Truzzi, 1991; see also Nicholson, 1979); her assertion cannot be substantiated.

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spective analysis the geoprofile located his home in only 0.08% of the total hunting area. However, this still translated into a region of 1.4 square kilometres (0.6 mi2), or approximately 1130 households and 3400 people. Suspects can be prioritized in such a situation, but resource limitations make door-to-door canvassing, for example, unfeasible. In other words, tactics and analysis must be harmonious.

The utility of the CGT model is demonstrated by the various geograph- ically-based investigative strategies that this process makes possible. Some examples of such applications include suspect prioritization by address, directed patrol saturation tactics, and the retrieval of computerized database information on the basis of location, licence plate registration, telephone number, and postal or zip code. These and other examples are discussed in the following chapter.

10.4 Geographic Profiling

Clues derived from crime site location and place can be of significant assistance to law enforcement agencies in the investigation of repetitive offences. “Locating where an offender might be is the cornerstone of any detective work ... and provides the foundations from which discovery of the criminal’s identity may proceed” (Canter, 1994, p. 282). The probable spatial behaviour of the offender may be determined from information contained in crime site locations, their geographic connections, and the characteristics and demography of the surrounding neighbourhoods.

Criminal apprehension efforts are assisted when some idea of offender residence area exists. This information allows police departments to focus their investigative activities, prioritize suspects, and concentrate saturation patrol efforts in those zones where the criminal predator is most likely to reside. Such investigative approaches are part of geographic profiling (Rossmo, 1992, 1993a, 1995a).

Geographic profiling is a strategic information management system designed to support serial violent crime investigations. It is part of the police behavioural science response, and has relationships to both linkage analysis and psychological profiling. It meets the definition of offender profiling: “an approach to police investigations whereby an attempt is made to deduce a description of an unknown offender based on evaluating minute details of the crime scene, the victim, and other available evidence” (Copson, 1995, p. 1; see also Dale, 1996). Not all types of offenders or crimes can be geographically profiled, but in appropriate cases the process produces practical results.

Geographic profiling is a police-provided service for law enforcement agencies or prosecuting offices, available upon official request (MacKay,

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1994). The first such profile was prepared in 1990. To date, requests have come from a variety of federal, provincial, state, and local law enforcement agencies, including the RCMP, the FBI, and Scotland Yard. The cases involve crimes of serial murder, serial rape and sexual assault, serial arson, serial robbery, serial exposers, sexual homicide, and kidnapping.

The implementation of geographic profiling within the policing community is a direct result of the SFU study on target patterns of serial murderers. This is an example of criminological research, done in an academic university setting, having practical policy and procedural implications for the criminal justice system. While the original research focused on serial killers, the hunting patterns of serial rapists, arsonists, and other repetitive violent offenders are similar and can also be geographically profiled. This resemblance is not surprising considering what the relevant theory tells us. Murder and violent sex crimes comprise the two single largest categories in geographic profiling casework, followed by arson and robbery.

10.4.1 Profiling Considerations

A geographic profile is only one part of what is usually a large and complex police investigation. Understanding its role in the overall picture and its relationship to other behavioural science methods is helpful. The following sequence outlines how geographic profiling typically fits into a criminal investigation:

1.Occurrence of a crime series;

2.Traditional investigative techniques;

3.Linkage analysis;

4.Criminal profile;

5.Geographic profile; and

6.New investigative strategies.

The ability to identify the existence of a serial offender is the starting point of the process. The extent and accuracy of the linkage analysis is important as the more crimes, the more accurate the geographic profile. But providing there is no spatial bias, and not too many locations are missed, unlinked crimes are not a critical problem. The CGT algorithm is also quite robust and its results are not significantly affected by the mistaken inclusion of an unconnected crime; generally, at least 90% of the information should be accurate.

If traditional investigative methods are successful, then there is unlikely to be a need for profiling. The development of new investigative strategies based on the profile is the topic of the following chapter. That leaves the relationship between geographic and psychological profiling.

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While primarily empirical, geographic profiling has both quantitative (objective) and qualitative (subjective) components. The objective component uses a series of geostatistical techniques and quantitative measures, such as the CGT program, to analyze and interpret the point pattern formed by target sites. Because the validity of these measures depends upon number of locations, they are inappropriate for smaller crime series. The subjective component of geographic profiling is based upon the reconstruction and interpretation of the offender’s mental map (Homant & Kennedy, 1998). A criminal profile is not a necessary precursor for a geographic profile, but the insights it provides to offender personality, behaviour, and lifestyle are useful, particularly in cases involving only a few locations. A geographic profile, in turn, helps refine a psychological profile, focus its application, and increase its utility. The two types of profiles optimize each other, and act in tandem to help investigators develop a “picture” of the person responsible for the crimes in question.

For example, in 1996 the RCMP investigated a series of 14 arsons of house carports in Burnaby, British Columbia, and requested psychological and geographic profiles. When a suspect who closely matched both profiles came to the attention of the investigator, he carefully focused on him, initiating surveillance and then interviewing strategies. The offender confessed. He closely matched the criminal profile, and literally lived across the street from the highest part of the geoprofile, in 0.6% of the hunting area (0.02 mi2).

Many different crime factors and environmental elements are considered in the construction and interpretation of a geographic profile. The most relevant ones include:

1.Crime locations — Offence locations and times are the most important data in a geographic profile. Also significant are the number and types of crime sites, their parsing, and the crime location set.

2.Offender type — The type and number of offender(s) affect crime geography. If multiple criminals living apart are involved, the geoprofile will focus on the dominant one’s residence. Large, amorphous gangs may not be suitable for geographic profiling because of changing group composition. Psychological profiling assists in interpreting offender behaviour by providing information on personality, background, and level of organization.

3.Hunting style — Criminal hunting methods influence both encounter and body dump site target patterns. Hunting style must be considered when preparing a geographic profile.

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4.Target backcloth — Constrained or patchy target backcloths limit the degree of offender choice, affecting the importance of certain crime site types for the profile.

5.Arterial roads and highways — People, including criminals, do not travel as the crow flies. Not only must they follow street layouts, but they are most likely to travel along major arterial routes, freeways, or highways.

6.Bus stops and rapid transit stations — Offenders without vehicles may use public transit or travel along bicycle and jogging paths. The locations and routes of these should be taken into consideration.

7.Physical and psychological boundaries — People are constrained by physical boundaries such as rivers, ocean, lakes, ravines, and highways. Psychological boundaries also influence movement. For example, a criminal of low socioeconomic status may avoid an upper class area, or a black offender might not wish to go into a white neighbourhood.

8.Zoning and land use — Zoning (e.g., residential, commercial, industrial) and land use (e.g., stores, bars, businesses, transportation centres, major facilities, government buildings, military institutions) provide keys as to why someone may be in a particular area. Police in Britain conduct site surveys and location inventories in the area surrounding a crime to help identify what may have brought an offender to a particular location. Similarly, information about the peak area in a geoprofile provides insight to a criminal’s anchor point, and zoning classification helps determine if this is a residence or workplace. For example, the geographic profile for a series of bank robberies occurring during the early afternoon pointed towards a commercially zoned area. Time and location factors correctly suggested an offender who was committing the crimes during his lunch break from work.

9.Neighborhood demographics — Some sex offenders prefer victims of a certain racial or ethnic group. These groups may be more common in certain neighbourhoods than in others, affecting spatial crime patterns.

10.Victim routine activities — The pattern of routine victim movements provides insight to how the offender is searching for targets.

11.Singularities — Single offences that do not appear to fit the overall pattern of the crime series may provide important clues and should be carefully reviewed.

12.Displacement — Media coverage or uniformed police presence can cause spatial displacement, affecting the locations of subsequent crime sites.

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Crime locations are the basis of a geographic profile, and a given murder can involve separate encounter, attack, murder, and body dump sites. But other locations that are not crime sites per se may also be connected to an offence. Examples of such locations include credit or bank card use, mailings, telephone calls, vehicle rentals or drops, witness sightings, and found property or evidence sites. In these cases, it may be possible to geographically profile a single crime, depending upon the number and types of locations.

In October 1995 two teenage girls in the municipality of Abbotsford, British Columbia, were attacked on the street at night by a man with a baseball bat. One victim was murdered and dumped in the Vedder Canal, some 20 miles away; the other was left for dead, but she somehow managed to revive and make her way to a nearby hospital. A few days later, the Abbotsford Killer began a series of bizarre actions starting with several taunting 911 telephone calls. He then stole and defaced the murder victim’s gravestone and dumped it in the parking lot of a local radio station. Finally, he threw a note wrapped around a wrench through a house window; in the note, he admitted to other sexual assaults. These actions provided 13 different sites for the geographic profile. He was eventually caught through a localbased strategy initiated by the Abbotsford Police Department. His residence was in the top 7.7% of the geoprofile (0.6 mi2).

A geoprofile may result in two peak areas, an indication the offender has more than one anchor point. Manley Eng, responsible for a series of arsons in Saanich and Victoria, British Columbia, left a crime pattern that resulted in dual peaks — one which contained his residence, and the other, his probation office. Information regarding land use, zoning, and area characteristics help interpret such outcomes. Examples of multiple anchor points include:

•Residence and work sites;

•Residence and social or family sites;

•Present and previous residences; and

•Two or more offenders living apart.

Between 1994 and 1998 the Mardi Gra Bomber was responsible for a total of 36 explosive devices, most in the Greater London area. These were mailed or delivered to locations near bank machines, supermarkets, payphones, businesses, and residences. Even though the targets and delivery methods varied, the underlying spatial pattern of the crimes remained consistent. Scotland Yard requested a geographic profile which produced two high probability regions; a primary area around Chiswick in west London, and a secondary peak in southeast London. When police detectives arrested two elderly brothers, it turned out they lived in Chiswick, and their family

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