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The purpose of this paper is to understand (i) how crime linkage is currently performed with residential burglaries in New Zealand, (ii) the factors that promote/hinder accurate crime linkage and (iii)whether computerised decision-support tools might assist crime linkage practice.

A total of 39 New Zealand Police staff completed a questionnaire/interview/focus group relating to the process, challenges, products and uses of crime linkage with residential burglary in New Zealand. These data (alongside four redacted crime linkage reports) were subjected to thematic analysis.

The data clearly indicated wide variation in crime linkage process, methods and products (Theme 1). Furthermore, a number of factors were identified that impacted on crime linkage practice (Theme 2).

Future research should develop computerised crime linkage decision-support tools and evaluate their ability to enhance crime linkage practice. Also, researchers should explore the use of crime linkage in court proceedings.

To overcome the barriers identified in the current study, greater training in and understanding of crime linkage is needed. Moreover, efforts to enhance the quality of crime data recorded by the police will only serve to enhance crime linkage practice.

By enhancing crime linkage practice, opportunities to reduce crime, protect the public and deliver justice for victims will be maximised.

The practice of crime linkage is under-researched, which makes it difficult to determine if/how existing empirical research can be used to support ongoing police investigations. The current project fills that gap by providing a national overview of crime linkage practice in New Zealand, a country where crime linkage is regularly conducted by the police, but no published linkage research exists.

Case linkage theory and practice have received growing empirical support; however, they have yet to be examined fully within Australia. For sexual assault case linkage to be successful, it is assumed that a serial rapist will behave relatively consistently across offences yet distinctively compared to other offenders. The purpose of this paper is to test the underlying principles of case linkage, behavioural consistency and distinctiveness, as well as distinguishing accuracy.

In total, 250 solved stranger rapes by 171 offenders (46 serial rapists, 125 one-off rapists) were taken from Queensland Police Service (QPS) crime records. All possible crime pairings were created and cross-crime similarity was assessed using Jaccard’s coefficient. Receiver operating characteristics (ROC) analysis was used to examine the ability to distinguish between linked and unlinked offence pairs.

Serial linked pairs had the highest Jaccard’s coefficient (0.456), followed by non-serial unlinked (0.253) and finally, serial unlinked pairs (0.247). Within the ROC analysis, an area under the curve value was found of 0.913, indicating excellent distinguishing accuracy. Both the underlying principles of behavioural consistency and distinctiveness were supported through theoretical and practical methods. This paper provides the first analysis of serial rape case linkage in Australia, adding validity to this practice.

The authors wish to acknowledge the support and assistance from the QPS in undertaking this research. The views expressed in this publication are not necessarily those of the QPS and any errors of omission or commission are the responsibility of the authors.

This paper provides validity to the practice of case linkage using a database within Australia. The results of this paper can be used to inform investigators of serial offender behaviours. The theories of offender consistency and distinctiveness are supported, highlighting the importance of behavioural evidence for practitioners. This paper provided a practical increase of the quantity and quality of offences uploaded on the Australian violent and sexual crimes database, which will assist further linkage efforts.

This paper is the first in Australia to examine consistency, distinctiveness and case linkage of serial stranger rape. Thus is contributes significantly not only to an increased understanding of serial rape and case linkage in Australia but also brings Australia closer to modern research practices in this field.

The Violent Crime Linkage Analysis System (ViCLAS) is a computerised database which is used by law enforcement in several countries to find potential links between serial violent crimes. In 2012, Bennell, Snook, MacDonald, House and Taylor identified a number of assumptions that must be valid for these computerised systems to be effective.

This paper revisits and expands on these assumptions with specific reference to the use of ViCLAS, looking at research that has been conducted since this 2012 review and outlining where research is still outstanding.

The importance of evaluating ViCLAS is highlighted in this paper.

Particularly, the research agenda highlights how the practice of comparative case analysis when using ViCLAS could be improved.

To the best of the authors’ knowledge, this is the first review of the research dedicated specifically to the evaluation of ViCLAS.

Crime linkage analysis (CLA) can be applied in the police investigation-phase to sift through a database to find behaviorally similar cases to the one under investigation and in the trial-phase to try to prove that the perpetrator of two or more offences is the same, by showing similarity and distinctiveness in the offences. Lately, research has moved toward more naturalistic settings, analyzing data sets that are as similar to actual crime databases as possible. One such step has been to include one-off offences in the data sets, but this has not yet been done with homicide. The purpose of this paper is to investigate how linking accuracy of serial homicide is affected as a function of added hard-to-solve one-off offences.

A sample (N = 117–1160) of Italian serial homicides (n = 116) and hard-to-solve one-off homicides (n = 1–1044, simulated from 45 cases) was analyzed using a Bayesian approach to identify series membership, and a case by case comparison of similarity using Jaccard’s coefficient. Linking accuracy was evaluated using receiver operating characteristics and by examining the sensitivity and specificity of the model.

After an initial dip in linking accuracy (as measured by the AUC), the accuracy increased as more one-offs were added to the data. While adding one-offs made it easier to identify correct series (increased sensitivity), there was an increase in false positives (decreased specificity) in the linkage decisions. When rank ordering cases according to similarity, linkage accuracy was affected negatively as a function of added non-serial cases.

While using a more natural data set, in terms of adding a significant portion of non-serial homicides into the mix, does introduce error into the linkage decision, the authors conclude that taken overall, the findings still support the validity of CLA in practice.

This is the first crime linkage study on homicide to investigate how linking accuracy is affected as a function of non-serial cases being introduced into the data.

The purpose of this paper was to compare the accuracy of linking crimes using geographical proximity between three distance measures: Euclidean (distance measured by the length of a straight line between two locations), Manhattan (distance obtained by summing north-south distance and east-west distance) and the shortest route distances.

A total of 194 cases committed by 97 serial residential burglars in Aomori Prefecture in Japan between 2004 and 2015 were used in the present study. The Mann–Whitney U test was used to compare linked (two offenses committed by the same offender) and unlinked (two offenses committed by different offenders) pairs for each distance measure. Discrimination accuracy between linked and unlinked crime pairs was evaluated using area under the receiver operating characteristic curve (AUC).

The Mann–Whitney U test showed that the distances of the linked pairs were significantly shorter than those of the unlinked pairs for all distance measures. Comparison of the AUCs showed that the shortest route distance achieved significantly higher accuracy compared with the Euclidean distance, whereas there was no significant difference between the Euclidean and the Manhattan distance or between the Manhattan and the shortest route distance. These findings give partial support to the idea that distance measures taking the impact of environmental factors into consideration might be able to identify a crime series more accurately than Euclidean distances.

Although the results suggested a difference between the Euclidean and the shortest route distance, it was small, and all distance measures resulted in outstanding AUC values, probably because of the ceiling effects. Further investigation that makes the same comparison in a narrower area is needed to avoid this potential inflation of discrimination accuracy.

The shortest route distance might contribute to improving the accuracy of crime linkage based on geographical proximity. However, further investigation is needed to recommend using the shortest route distance in practice. Given that the targeted area in the present study was relatively large, the findings may contribute especially to improve the accuracy of proactive comparative case analysis for estimating the whole picture of the distribution of serial crimes in the region by selecting more effective distance measure.

Implications to improve the accuracy in linking crimes may contribute to assisting crime investigations and the earlier arrest of offenders.

The results of the present study provide an initial indication of the efficacy of using distance measures taking environmental factors into account.

Traditional crime linkage studies on serial sexual assaults have relied predominantly on a binary crime linkage approach that has yielded successful results in terms of linkage accuracy. Such an approach is a coarse reflection of reality by focussing mainly on the outcome of an offence, neglecting the forceful differences due to the intricate offender-victim interaction. Only few researchers have examined sexual assaults through the lens of a sequence analysis framework. This paper aims to present the first empirical test of offence sequence-based crime linkage, moving beyond exploratory analyses.

Offence accounts from 90 serial sexual assault and rape victims from the UK were analysed and sequentially coded. Sequence analysis allowed to compare all offences combinations regarding their underlying sequence of events. The resulting comparison was transformed and plotted in two-dimensional space by multidimensional scaling analysis for a visual inspection of linkage potential. The transformed proximities of all offences were used as predictors in a receiver operating characteristic analysis to actually test their discriminatory accuracy for crime linkage purpose.

Sequence analysis shows significant discriminatory accuracy for crime linkage purpose. However, the method does perform less well than previous binary crime linkage studies.

Several limitations due to the nature of the data will be discussed.

The practical limitations are as follows: the study is a potential practical value for crime analysts; it is a complimentary methodology for statistical crime linkage packages; it requires automated coding to be useful; and it is very dependent on crime recoding standards.

The exploratory part of this study has been published in a book chapter in 2015. However, to the best of the authors’ knowledge, the succinct test of crime linkage accuracy is the first of its kind.

The purpose of this paper is to explore the differences (if any) between serial and hard-to-solve one-off homicides, and to determine if it is possible to distinguish the two types of homicides based on offence behaviours and victim characteristics.

A sample of 116 Italian serial homicides was compared to 45 hard-to-solve one-off homicides. Hard-to-solve one-off homicides were defined as having at least 72 hours pass between when the offence came to the knowledge of the police and when the offender was caught. Logistic regression was used to predict whether a killing was part of a series or a one-off offence.

The serial killers targeted more strangers and prostitutes, displayed a higher level of forensic awareness both before and after the killing, and had more often an apparent sexual element in their offence. Conversely, the one-off homicides were found to include more traits indicative of impulsive and expressive behaviour. The model demonstrated a good ability (AUC=0.88) to predict whether a homicide belonged to the serial or one-off category.

The findings should be replicated using local homicide data to maximise the validity of the model in countries outside of Italy.

Being able to distinguish between serial and one-off homicides based on information available at a new crime scene could be practically useful for homicide investigators managing finite resources.

Studies comparing serial homicides to one-off homicides are scarce, and there are no studies explicitly trying to predict whether a homicide is an isolated case or part of a series.

The purpose of this paper is to identify offender typologies based on aspects of the offenders’ psychopathology and their associations with crime scene behaviours using data derived from the National Confidential Enquiry into Suicide and Safety in Mental Health concerning homicides in England and Wales committed by offenders in contact with mental health services in the year preceding the offence (n=759).

The authors used multiple correspondence analysis to investigate the interrelationships between the variables and hierarchical agglomerative clustering to identify offender typologies. Variables describing: the offenders’ mental health histories; the offenders’ mental state at the time of offence; characteristics useful for police investigations; and patterns of crime scene behaviours were included.

Results showed differences in the offenders’ histories in relation to their crime scene behaviours. Further, analyses revealed three homicide typologies: externalising, psychosis and depression.

These typologies may assist the police during homicide investigations by: furthering their understanding of the crime or likely suspect; offering insights into crime patterns; provide advice as to what an offender’s offence behaviour might signify about his/her mental health background. Findings suggest information concerning offender psychopathology may be useful for offender profiling purposes in cases of homicide offenders with schizophrenia, depression and comorbid diagnosis of personality disorder and alcohol/drug dependence.

Empirical studies with an emphasis on offender profiling have almost exclusively focussed on the inference of offender demographic characteristics. This study provides a first step in the exploration of offender psychopathology and its integration to the multivariate analysis of offence information for the purposes of investigative profiling of homicide by identifying the dominant patterns of mental illness within homicidal behaviour.

The present study aims to examine the scope and contribution of behavioural investigative advice (BIA) reports from the National Crime Agency (NCA).

The 77 BIA reports reviewed were written between 2016 and 2021. They were evaluated using Toulmin’s (1958) strategy for structuring pertinent arguments, current compliance with professional standards, the grounds and backing provided for the claims made and the potential utility of the recommendations provided.

Consistent with previous research, most of the reports involved murder and sexual offences. The BIA reports met professional standards with extremely high frequency. The 77 reports contained a total of 1,308 claims of which 99% were based on stated grounds. A warrant and/or backing was provided for 73% of the claims. Most of the claims in the BIA reports involved a behavioural evaluation of the crime scene and offender characteristics. The potential utility of the reports was judged to be 95% for informative behavioural crime scene analysis and 40% for potential new lines of enquiry.

The reports should serve as a model for the work of behavioural investigative advisers internationally.

To the best of the authors’ knowledge, this is the first study to systematically evaluate BIA reports commissioned by the NCA; it adds to previous similar studies by evaluating the largest number of BIA reports ever reviewed, and uniquely provides judgement of overall utility.