Linking Crimes Using Behavioural Clues: Current Levels of Linking Accuracy and Strategies for Moving Forward

The number of published studies examining crime linkage analysis has grown rapidly over the last decade, to the point where a special issue of this journal has recently been dedicated to the topic. Many of these studies have used a particular measure (the area under the receiver operating characteristic curve, or the AUC) to quantify the degree to which it is possible to link crimes. This article reviews studies that have utilised the AUC and examines how good we are currently at linking crimes (within the context of these research studies) and what factors impact linking accuracy. The results of the review suggest that, in the majority of cases, moderate levels of linking accuracy are achieved. Of the various factors that have been examined that might impact linking accuracy, the three factors that appear to have the most significant impact are crime type, behavioural domain, and jurisdiction. We discuss how generalisable these results are to naturalistic investigative settings. We also highlight some of the important limitations of the linking studies that we reviewed and offer up some strategies for moving this area of research forward. Copyright © 2013 John Wiley & Sons, Ltd.     

The practice of crime linkage: A review of the literature

Crime linkage has been the subject of increasing attention in academic research. Research has found support for the principles of behavioural consistency and distinctiveness, which underpin crime linkage, but this does not provide direct evidence as to whether crime linkage is useful in practice. This literature review draws together documentation that refers to the practice of crime linkage, from assessing analysts' efficacy, to discussing the usage of computerised tools to assist with the linkage process, to providing a comprehensive outline of the process itself. The implications of the amount and type of information currently available are discussed, including the variations in practice and terminology that were explored. Avenues for future investigation and the manner in which future research could be conducted are set out in a research agenda.     

The consistency of inconsistency in serial homicide: patterns of behavioural change across series

Linkage analysis is a crucial part of the investigative process when faced with a possible series of related offences. Establishing behavioural consistency (i.e., offender's behaviours consistently present across the series) is at the core of linkage. Recent empirical studies have found little evidence of consistency looking at either individual or groups of behaviours in serial homicide. It is argued that behavioural changes are rooted in the changing cognitive strategies that offenders use to reach their ultimate goal (i.e. the commission of multiple homicides). Factors that could account for these changes include learning, situational factors, loss of control, and changes in the offender's fantasy. Patterns of behavioural change have been identified in serial crimes, such as rape. However, no empirical studies have looked at patterns of behavioural change in serial homicide. The present study examined patterns of consistency and change using a combination of thematic and behavioural subgroup approaches that use Multidimensional Scaling. Thematic differentiation indicative of behavioural manifestations of cognitive strategies was found in all three examined subgroups: planning, wounding, and offender–victim interaction, and patterns of change within these subgroups provided support for the above theories. Looking at behavioural patterns rather than individual behaviours, may be a more fruitful way of examining consistency in serial homicide, and could have significant implications for linkage analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

From marine ecology to crime analysis: Improving the detection of serial sexual offences using a taxonomic similarity measure

Jaccard has been the choice similarity metric in ecology and forensic psychology for comparison of sites or offences, by species or behaviour. This paper applies a more powerful hierarchical measure—taxonomic similarity (Δ_s), recently developed in marine ecology—to the task of behaviourally linking serial crime. Forensic case linkage attempts to identify behaviourally similar offences committed by the same unknown perpetrator (called linked offences). Δ_s considers progressively higher‐level taxa, such that two sites show some similarity even without shared species. We apply this index by analysing 55 specific offence behaviours classified hierarchically. The behaviours are taken from 16 sexual offences by seven juveniles where each offender committed two or more offences. We demonstrate that both Jaccard and Δ_s show linked offences to be significantly more similar than unlinked offences. With up to 20% of the specific behaviours removed in simulations, Δ_s is equally or more effective at distinguishing linked offences than where Jaccard uses a full data set. Moreover, Δ_s retains significant difference between linked and unlinked pairs, with up to 50% of the specific behaviours removed. As police decision‐making often depends upon incomplete data, Δ_s has clear advantages and its application may extend to other crime types. Copyright © 2007 John Wiley & Sons, Ltd.     

Linking property crime using offender crime scene behaviour: A comparison of methods

This study compared the ability of seven statistical models to distinguish between linked and unlinked crimes. The seven models utilised geographical, temporal, and modus operandi information relating to residential burglaries (n = 180), commercial robberies, (n = 118), and car thefts (n = 376). Model performance was assessed using receiver operating characteristic analysis and by examining the success with which the seven models could successfully prioritise linked over unlinked crimes. The regression‐based and probabilistic models achieved comparable accuracy and were generally more accurate than the tree‐based models tested in this study. The Logistic algorithm achieved the highest area under the curve (AUC) for residential burglary (AUC = 0.903) and commercial robbery (AUC = 0.830) and the SimpleLogistic algorithm achieving the highest for car theft (AUC = 0.820). The findings also indicated that discrimination accuracy is maximised (in some situations) if behavioural domains are utilised rather than individual crime scene behaviours and that the AUC should not be used as the sole measure of accuracy in behavioural crime linkage research.     

The Jack the Ripper murders: a modus operandi and signature analysis of the 1888–1891 Whitechapel murders

A number of females, commonly recognized as 11 victims, were murdered in separate events in Whitechapel, London between 1888 and 1891. An evaluation of the murders revealed that six of those murders were linked by a number of distinct, personal signature characteristics, including picquerism, overkill, incapacitation, domination and control, open and displayed, unusual body position, sexual degradation, mutilation, organ harvesting, specific areas of attack, preplanning and organization, and a combination of signature features. The signature characteristics observed in these infamous Jack the Ripper murders were compared to a 1981–1995 cohort of 3359 homicide cases from Washington State's HITS database. The analysis revealed that the signature displayed in six of the Whitechapel murders was extremely rare. There were only six records of female victims, one a prostitute, with probed, explored, or mutilated body cavities. There were only two cases, both females who were not prostitutes, where the body was left in an unusual position and body cavities were explored, probed, or mutilated. Copyright © 2005 John Wiley & Sons, Ltd.     

Linkage Analysis as Evidence in Court: A Thematic Analysis of Mock Juror Deliberations

Linkage analysis has, albeit occasionally, been presented in courts across the world as evidence that a series of offences possess behavioural similarities and distinctiveness from other offences, meaning they have probably been committed by the same individual. It is therefore imperative to ascertain how linkage analysis is regarded by juries within the context of deliberations. Three groups of participants (N = 22) eligible for jury duty in England and Wales viewed a simulated rape and murder trial derived from an actual South African case. Linkage analysis formed the sole evidence against the defendant in the two later offences, although DNA matches and eyewitness identifications of the defendant were present in the two earlier offences. Participant deliberations were recorded and subjected to thematic analysis. Five themes were discovered: behavioural consistencies and inconsistencies, physical versus case linkage evidence, barriers to admissibility, potential uses of linkage analysis, and dependence of lay knowledge. Jurors' over‐reliance on erroneous lay knowledge contributed to their conclusion that linkage analysis is, at present, unrepresentative evidence that cannot independently indicate a defendant's culpability. However, participants believed that linkage analysis could be a useful tool within investigations and, with further research evidence, in court in England and Wales. Copyright © 2014 John Wiley & Sons, Ltd.     

Commuters and marauders: an examination of the spatial behaviour of serial criminals

The demographic characteristics of serial offenders that distinguish between the commuter and the marauder offence styles were examined. Proposed by Canter and Larkin (1993) these two styles represent competing models of criminal spatial behaviour under which the home base plays a role in offence site selection. Data on serial burglars, arsonists and sex offenders were extracted from the criminal records maintained by the NSW Police Service. The offence style of each offender's crime series was identified in order to relate the offence style to the demographic variables, and to examine the offender's first and last offences in a series. A commuter offence style was more likely to be adopted by burglars and generally by adult males. A marauding offence style was apparent in sex offenders and metropolitan based offenders. There was a progression in the distance travelled to offend across all crime types, as the last offence was located further from the home base by comparison with the first. These findings serve to validate the conceptual distinction between commuter and marauder offence styles. Several implications for further research are addressed. Copyright © 2004 John Wiley & Sons, Ltd.     

Predicting sugar-sweetened behaviours with theory of planned behaviour constructs: Outcome and process results from the SIPsmartER behavioural intervention

Objective: Guided by the theory of planned behaviour (TPB) and health literacy concepts, SIPsmartER is a six-month multicomponent intervention effective at improving SSB behaviours. Using SIPsmartER data, this study explores prediction of SSB behavioural intention (BI) and behaviour from TPB constructs using: (1) cross-sectional and prospective models and (2) 11 single-item assessments from interactive voice response (IVR) technology.

Design: Quasi-experimental design, including pre- and post-outcome data and repeated-measures process data of 155 intervention participants.

Main Outcome Measures: Validated multi-item TPB measures, single-item TPB measures, and self-reported SSB behaviours. Hypothesised relationships were investigated using correlation and multiple regression models.

Results: TPB constructs explained 32% of the variance cross sectionally and 20% prospectively in BI; and explained 13–20% of variance cross sectionally and 6% prospectively. Single-item scale models were significant, yet explained less variance. All IVR models predicting BI (average 21%, range 6–38%) and behaviour (average 30%, range 6–55%) were significant.

Conclusion: Findings are interpreted in the context of other cross-sectional, prospective and experimental TPB health and dietary studies. Findings advance experimental application of the TPB, including understanding constructs at outcome and process time points and applying theory in all intervention development, implementation and evaluation phases.     

Classification of Planning and Violent Behaviours in Serial Homicide: A Cross‐National Comparison Between South Africa and the US

Recent literature suggests that different ‘styles’ of homicide will most appropriately be reflected in the different types of behaviours committed by offenders during the crime. In the last few years, there has been a move to standardise classification systems of single homicides and establish their cross‐national generalisability. Literature on serial homicide to date has mostly centred on homicides occurring in the US. However, national differences due to factors such as culture, national identity, political, and socio‐economic circumstances may decrease the applicability of these models or certain aspects thereof in other countries and thus must be evaluated. The present study tested the applicability in the South African context of a recently developed US‐based serial homicide crime scene classification framework. Specifically, this study compared the thematic differentiation in planning and violent behaviours that the offenders engage in and how this differentiation compares with that in the US. The sample consisted of 25 homicides that were in total responsible for the murder of 267 victims. Results indicated that overall, the framework is useful and applicable in the South African sample, but important environmental and contextual constraints must be taken into account. Copyright © 2014 John Wiley & Sons, Ltd.     

Sleep hygiene behaviours: An application of the theory of planned behaviour and the investigation of perceived autonomy support,past behaviour and response inhibition

This study investigated the sleep hygiene behaviour of university students within the framework of the Theory of Planned Behaviour (TPB [Ajzen, I. (1991). The theory of planned behavior. Organizational Behavior and Human Decision Processes, 50, 179–211.]), and examined the predictive validity of additional variables including perceived autonomy support, past behaviour and response inhibition. A total of 257 undergraduate students from an Australian university were administered two online questionnaires at two time points. At time 1, participants completed the TPB questionnaire and the Go/NoGo task as a measure of response inhibition. A week later at time 2, participants completed a questionnaire measuring the performance of sleep hygiene behaviours. Multiple and hierarchical regression analyses showed that the TPB model significantly predicted intention and behaviour. Although intention and perceived behavioural control were statistically significant in predicting behaviour, past behaviour and response inhibition accounted for more variance when added to the TPB model. Subjective norm was found to be the strongest predictor of intention implying the importance of normative influences in sleep hygiene behaviours. Response inhibition was the strongest predictor of behaviour, reinforcing the argument that the performance of health protective behaviours requires self-regulatory ability. Therefore, interventions should be targeted at enhancing self-regulatory capacity.     

Conceptualization and measurement of temporal focus: The subjective experience of the past,present, and future

Temporal focus is the attention individuals devote to thinking about the past, present, and future, and the concept is important because it affects how people incorporate perceptions about past experiences, current situations, and future expectations into their attitudes, cognitions, and behavior. However, temporal focus has not been clearly defined nor situated in a nomological network of constructs. In addition, existing measures of temporal focus suffer from various shortcomings. In this paper, we advance the concept of temporal focus by critically examining its conceptualization, developing a new measure of temporal focus (Temporal Focus Scale; TFS), and evaluating the validity (i.e., construct, convergent, discriminant, nomological, and predictive validity) of the TFS across four studies. We conclude that understanding how individuals focus their attention toward the past, present, and future clarifies their responses to explicit and implicit temporal information, which suggests that a variety of research streams would benefit from incorporating the concept of temporal focus.