problem-oriented policing (Brantingham & Brantingham, 1981b; Brantingham & Jeffery, 1981; R. V. Clarke, 1992, 1997; Felson, 1986; Goldstein, 1990; Lowman, 1986; Smith, 1986). Work in such areas has provided the conceptual foundations for geographic profiling.

7.1 Geography and Crime Studies

Geographical patterns in crime have been noted since the mid-19th century pioneering work of Andre-Michel Guerry and Lambert-Adolphe Quetelet who mapped, on a national basis, violent and property offences and examined their spatial relationship to poverty (Brantingham & Brantingham, 1981c; Vold & Bernard, 1986). The most famous spatial crime studies were conducted in the early 20th century, when the city of Chicago served as an inspiration source and a field of experimentation for University of Chicago sociologists (Warren, 1972; Williams & McShane, 1988). The geographical focus of criminology had shifted from regional areas to city neighbourhoods.

The Chicago School’s human ecology and theories of urban growth, developed by Robert Park and Ernest Burgess, served as guides for former probation officer Clifford R. Shaw and his colleague Henry D. McKay (Brantingham & Brantingham, 1984; Vold & Bernard, 1986). While working for the Illinois Institute for Juvenile Research, Shaw and McKay examined a plethora of urban social ills, including the politically important issue of crime (Williams & McShane, 1988; Wilson, 1984). Much of this study was done along the margins of society; researchers observed, talked to, and examined criminals, gang members, hoboes, immigrants, and slum dwellers. Most importantly, they did this within the “natural” urban contexts associated with the people they were studying. This attempt to triangulate the subjective human perspective with more objective demographic statistics exemplified the work of the Chicago School (Smith, 1986).

While there is a long tradition of spatial crime analysis, the ultimate units of concern are individual human beings and their day-to-day social interactions, not census statistics or demographic data. This point seems to have been forgotten during the unfruitful positivistic geographic research of the 1960s, when complicated but theoretically weak factor analytic methods were used to correlate a spectrum of spatially distributed variables (Smith, 1986).

Recent developments in the spatial study of crime have been more promising. The integration of geographical perspectives, urban planning tactics, environmental criminology, and ecological approaches based on econometric studies has led to a series of interesting studies (Brantingham & Brantingham, 1981a; Lowman, 1986; Smith, 1986). While the field has been primarily instrumentalist in nature, writers such as Lowman and Smith have com-

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•Most cities contain high crime rate neighbourhoods, the arrangement and location of which influence the patterning of crime trips (Gabor & Gottheil, 1984; Rhodes & Conly, 1981).

A crime trip, or the journey to crime, is usually defined by some direct or surrogate measure of distance between offender residence and location of offence. This may or may not have been the actual journey taken by the offender who could have originated his or her travel from work, the house of a friend, or the local bar. For example, in Pettiway’s (1995) study of Philadelphia crack cocaine users, 25.7% originated their drug buying trip from home, with street corners and outside hangouts (22.9%), friends and relatives (10.7%), shopping and business (10.8%), recreation (7.4%), and other places (22.4%) comprising the remaining origins. Of significance, however, is the finding that, regardless of origin, most destinations were in the offender’s neighbourhood (61%). Almost all trips (93%) began and ended within the city limits of Philadelphia. These results “suggest that even when individuals engage in activities away from their places of residence, they tend to return to locations near those places” (p. 515).

In a study of robbery in northern California, Feeney (1986, 1996) found 70% of offenders robbed in their home towns, and over one third in their own neighbourhoods. Of the 30% who offended in a different town, only half went there to commit a robbery; the rest were there for some other reason. Those who commute to rob almost always choose a contiguous town. Robbery is a casually planned crime, and the study found fewer than 5% of offenders make detailed plans such as observing the layouts of prospective targets, establishing contingencies, or predetermining escape routes (Feeney, 1986). Victims are chosen because of convenience, appearance of money, low risk, and the possibility of a fast getaway. Or, in the words of one robber, “‘Just where we happened to be, I guess’” (p. 92).

Canter and Gregory (1994) analyzed crime trip patterns for 45 serial rapists responsible for 251 offences committed during the 1980s in Greater London and Southeast England. The mean number of rapes per offender in this sample was 5.6 (standard deviation = 3.6), with a minimum of 2 and a maximum of 14. It was theorized that offenders with greater access to resources will exhibit longer journeys to crime. Therefore, rapists with more geographic knowledge, money, and time have the capability of travelling further distances to commit their crimes. Canter and Gregory (1994) propose that criminals with greater resources (geographic knowledge, financial, time) travel further to offend. They analyzed crime trip distances for a sample of serial rapists using dichotomized parameters of race, venue, weekday, and offender age. It was suggested an expert system for determining area of criminal residence could be based upon this approach. The basic viability of

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the system remains unknown, however, as the study negated its results by using the same data set for both learning and testing.

White rapists were found to travel further to commit their crimes than black rapists, the latter having an 80% chance of living within a half mile of one of their offences. Rapists who chose outside venues typically journeyed 2.7 times as far as those who chose inside or mixed venues. Weekend rapists averaged minimum crime trip distances 2.5 times as great as weekday offenders, though this difference was not statistically significant. Older rapists (over 25 years of age) appeared to travel further than younger rapists, but this finding also was not statistically significant. The percentages for each group found to have travelled under a half mile from their home base to their first known offence were: blacks, 74%; whites, 18%; inside/mixed, 70%; outside, 28%; weekday, 41%; weekend, 50%; mixed, 60%; under 25 years of age, 54%; over 25 years of age, 38%; and total, 47%.

Results from journey-to-crime studies are usually reported in one of four manners: (1) mean crime trip distances; (2) medial circles; (3) mobility triangles; and (4) distance-decay functions. Studies using mean crime trips compute the arithmetic average for the distance travelled by offenders from home to offence location. Some researchers employ the geometric mean to avoid the distortion of extreme values (LeBeau, 1987a), while others use additional descriptive statistics such as the mode (Rhodes & Conly, 1981), maximum crime trip distance (Canter & Larkin, 1993), minimum crime trip distance (Warren et al., 1995), range (Turner, 1969), and directional information (Rengert & Wasilchick, 1985).

The major problem with the use of the mean or mode is the limited information a univariate statistic provides. The mean is also susceptible to the influence of spatial outliers and may say little about the typical journey. And as an average distance is produced from an aggregation of trips involving several offenders, it might not accurately describe any one type of offender.

Studies using medial circles define a radius containing a certain percentage of offences.34 In a study of robbery within Boston, Reppetto (1976) found 90% of the offences occurred within 1.5 miles of the offender’s residence. As with mean crime trips, medial circles supply only a single measure of crime journeys, says little of the typical crime trip, and expresses almost nothing about cases that fall outside of the set radius.

Mobility triangles were first used by Burgess (1925) to describe situations where offence location and offender residence were in different neighbourhoods; this was in contrast to neighbourhood triangles where the crime takes place in the offender’s home area. Subsequent developments of the mobility triangle concept adopted various combinations of crime scene, offender res-

34 If the circle contains one-half of the offences, the radius is equivalent to the median crime trip distance.

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idence, and victim residence spatial conjunction (Amir, 1971; Normandeau, 1968). Crime journey research findings are often presented in the form of the percentage of offences that fit into the neighbourhood triangle (Ploughman & Ould, 1990; Rand, 1986).

Research using neighbourhood or mobility triangles raises the question of how to define the concept of “neighbourhood.” Census tract delineations are often used, but this is a problematic assumption. Census tracts are only rough approximations of neighbourhoods and more sophisticated concepts of mobility, routine activities, and target selection are available (e.g., Brantingham & Brantingham, 1981; Felson, 1986). Other studies do not define the concept of neighbourhood, but rather use the subjective interpretations of respondents (see, for example, DeFrances & Smith, 1994).

The most useful presentation of crime trip data is the distance-decay approach, a graphical curve that shows the number of trips for several different radii (e.g., half-mile increments) from the offender’s residence (see, for example, Capone & Nichols, 1976; Rhodes & Conly, 1981; also Baldwin & Bottoms, 1976). Such formats allow for an inspection of the distance-decay function, providing more information for further analysis and a fuller understanding of the nature of crime journeys.

Van Koppen and de Keijser (1997) have questioned the accuracy of distance decay findings in the journey-to-crime literature. Using randomly generated data that lacked distance decay, they were able to show the aggregation of individual crime trips led to a distance-decay result. Their main point is correct. Individual behaviour cannot be safely inferred from aggregate data, an error referred to as the ecological fallacy.

Research at a certain spatial level of analysis may produce conclusions that, while valid at that scale, are invalid at different levels (Goodall, 1987). When research arguments are made by relating results derived from one geographic level of analysis to another, an ecological fallacy occurs. This usually involves the application of correlates derived from areal data to individuals, though an ecological fallacy can occur by moving in either direction through the spatial analytic framework (Brantingham & Brantingham, 1984). The scale problem, as geographers refer to it, can be a serious difficulty for attempts to generalize from geographical areal research as changes in focus may mask the true nature of relationships (Langbein & Lichtman, 1978; Taylor, 1977).

For example, combining individual crime trip distances without first standardizing the data35 often obscures the existence of the buffer zone. The method of van Koppen and de Keijser, however, actually created non-random distances with a bias towards shorter crime trips, therefore introducing

35 One method of standardization is to divide every individual crime trip distance by the offender’s mean crime trip distance.

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distance decay (Rengert, Piquero, & Jones, 1999). True random data would show a uniform distribution. They also did not distinguish between studies of destination and origin distance decay. Finally, they ignored research that properly established distance decay in serial criminals (e.g., Davies & Dale, 1995b; Rossmo, 1995b; Sapp et al., 1994; Warren, Reboussin, Hazelwood, Cummings, Gibbs, & Trumbetta, 1998).

It has been suggested that as an offender’s criminal career matures, jour- ney-to-crime distances lengthen and size of hunting area increases (Brantingham & Brantingham, 1981; Canter & Larkin, 1993). After the arrest of David Berkowitz, police searching his apartment “found maps of Connecticut, New York, and New Jersey, marked and annotated in such a way that investigators took them as evidence that Berkowitz was planning to extend his killing grounds” (Time-Life Books, 1992b, p. 179). Hungarian Sylvestre Matuschka killed 22 people and injured 75 more in engineered train wrecks (Nash, 1992). Upon his apprehension in 1932, authorities seized railway schedules and maps for France, Italy, and The Netherlands – all part of his plan to cause future wrecks monthly (Seltzer, 1998).

The FBI believes that the first attack in a serial murder series is the one most likely to be closest to the offender’s home (Warren et al., 1995). Both Barrett (1990) and Canter (1994) note that the first crime of a serial offender may be spontaneous and impulsive, and victim selectivity tends to decrease over time (see, for example, the discussion on changes in Jeffrey Dahmer’s murder pattern, in Ressler & Shachtman, 1992). These observations indicate the importance of a temporal dimension in the analysis of spatial crime patterns (see Kind, 1987a; LeBeau, 1992; Newton & Newton, 1985; Newton & Swoope, 1987).

In an FBI study of travel distances and offence patterns for 108 U.S. serial rapists responsible for a total of 565 offences, Warren et al. (1995) observed that the rape closest to the offender’s residence was the first in 18%, but the fifth in 24% of the cases. A British study of 79 rapists and 299 sexual offences (Davies & Dale, 1995a) found no significant difference in distance between first and last crime trip for prolific offenders (those with five or more rapes). Noting that habitual burglars and robbers travelled longer distances, Davies and Dale (1995a) suggest that for those rapists with a history of break and entry, the first rape in a series might well be their fiftieth housebreaking. Any maturation in crime pattern would therefore have occurred long ago. This problem is compounded by the fact that sexual assaults are notoriously underreported, and the first known rape might actually be the offender’s second or third (Davies & Dale; Leyton, O’Grady, & Overton, 1992). Such a misinterpretation happened in the Vampire Killer case where Sacramento County police believed the second murder was actually the first (Ressler & Shachtman, 1992).

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The journey-to-crime concept implies a home base from which the trip commenced, yet some offenders may not have a residence. Convicted criminals also tend to be less residentially stable than noncriminals, and psychopaths in particular are nomadic. Rossmo found that a significant number of criminal fugitives in Canada are willing to travel thousands of miles to avoid prison (1987; Rossmo & Routledge, 1990). Marvell and Moody (1998) observed that a small but highly active group of major criminals were extremely mobile, for reasons that included fear of the police, conflicts with other criminals, or general wanderlust. These offenders engaged in a succession of road trips involving temporary stays in different regions, or permanent moves of residence every few months or years from one state to another. It is therefore important not to confuse transiency with crime trips.

Travelling offenders are in the minority, and fewer than 10% of the criminals Canter (1994) studied were of “no fixed abode” at the time of their arrest. Davies and Dale (1995b) determined that 22% of those rapists for whom they had such information were itinerant. Victims were confronted at their homes in 41% of the cases,36 and within public areas (including apartment building common areas) in 58% of the cases. They observed that “some rapists were obviously drawn to areas where potential victims were accessible, such as red-light districts ... The distance the offenders travelled was clearly related to the proximity of their own residence to these locations” (Davies & Dale, 1995a, p. 13).

These places of victim accessibility include both nodes (e.g., entrances to train stations or apartment blocks), and routes used by females commuting to work, school, shopping, and entertainment areas. Because the value of these “victim hunting grounds” depended upon female activity level, their desirability is influenced by time of day. Distinct clusters of contact sites were noted, some associated with victim availability, others with residences of people significant to the offender (Davies & Dale, 1995a). Ted Bundy’s FBI wanted poster alerted people to his preferred target areas — beaches, ski resorts, discotheques, and college campuses (Ressler & Shachtman, 1992). Such finding are consistent with Brantingham and Brantingham’s (1981, 1993b) pattern theory and model of crime site selection, discussed in the next section.

36 House (1993) examined offence venue for 61 Canadian cases of stranger sexual assault committed by 30 offenders (40% of whom were serial rapists, each responsible for an average of 2.8 crimes). He found 61% of the crimes occurred outdoors and 39% inside (38% of which were in the victim’s residence).

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Table 7.1 Journey–to–Crime Research3

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Table 7.1 Journey–to–Crime Research (Continued)

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Table 7.1 Journey–to–Crime Research (Continued)

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Table 7.1 Journey–to–Crime Research (Continued)

37NFA means no fixed address, and n/k, not known. Unless otherwise specified, the figures in the Crime Trip Distance column refer to mean journey-to-crime distance.

From Rossmo, D.K. (1995b). Multivariate spatial profiles as a tool in crime investigation. In C.R. Block, M. Dabdoub, & S. Fregly (Eds.). Crime analysis through computer mapping (pp. 65-97). Washington, DC: Police Executive Research Forum. Used with permission.

3.37

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