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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 article is to improve the use of evidence-based practice and research utilization in the offender profiling process. The use of offender profiling has been met with increasing resistance given its exaggerated accuracy. The “Investigative Journalist/Expert Field Micro Task Force” model, a collaborative method that incorporates offender profiling and is designed to address unresolved serial homicides, is introduced and evaluated alongside recommendations on attaining adherence.

The model was field tested in 17 instances. The measures used by the Federal Bureau of Investigation to gauge the usefulness of their case consultations, whether their input helped catch the offender, offer new leads, move the case forward, provide new avenues or give new ideas, were used to evaluate the model.

The model established likely patterns of serial murder activity among strangulations of women in Chicago, Cleveland, and Panama and resulted in convictions of suspects in Louisiana and Kansas City. This model is valuable when used to parse modern-day offenders from those who committed unresolved homicides as the latter display different behaviors that can make investigations difficult endeavors. Results from the field tests mirror those from the literature in that profiling alone did not result in the capture of serial killers. Instead, profiling was used in conjunction with other efforts and mainly as a means to keep the investigation moving forward.

Unresolved homicides are at a point of crisis and represent a significant but largely unaddressed societal problem. The success of this model may compel law enforcement to restore faith in offender profiling.

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.

Beginning with the understanding that healthcare serial killers differ from traditional serial killers in terms of victim selection, risk and offender behavior, this paper attempts to reconceptualize how the motivations of healthcare serial killers are understood within the scope of care‐giving environments.

Drawing on the current literature surrounding serial homicide and serial killers, the paper argues that healthcare serial killers, by virtue of their profession, have an advantage in committing homicides that are less likely to be detected.

It is found that healthcare professionals work in an environment that is conducive to anti‐social behaviour like homicide. More specifically, recurring conditions within the work place (e.g. lack of a reporting system for problem employees, code of silence amongst employees) adds to the ease with which healthcare serial killers can evade capture.

Research examining healthcare professionals who kill their patients is limited. The current paper provisionally adds to the current understanding of serial homicide. While offering various explanations as to why healthcare serial killers are difficult to detect, this paper also explores some potential solutions for the monitoring of healthcare professionals and protecting the vulnerable patients in their care.

Rapid sequence homicide offenders (RSHOs), formerly spree killers, are an understudied population due to the confusion surrounding their classification in relation to serial murderers. The paper aims to discuss this issue.

An exploratory, comparative analysis of 56 RSHOs and 60 serial murderers was conducted on US-based data from 2014 to 2018 derived from the Consolidated Serial Homicide Offender Database to determine similarities and differences between the cohorts.

RSHOs and serial murderers are similar in that they often kill their victims using a singular method, have limited mobility, kill a similar number of victims both known and unknown to them and are both supremely motivated by domestic anger. There is an inverse relationship between serial murderers and RSHOs: as one group increases in prevalence the other decreases.

In order to divert men into more pro-social activities, attention must be dedicated to increasing mental health services that provide them with the tools to diffuse their hatred and couple that with effective gun control strategies and ways to enhance the compromised anger management skills of a generation of volatile men.

Academicians have been hesitant to juxtapose these offenders but based this conclusion on surface-level differences. A reimagining of these categorical structures is needed. The once clear delineation between these cohorts may continue to shrink and synchronize until one subsumes the other.

Homicidal behaviour is influenced by a complex interaction of behavioural, situational and environmental factors that raise many challenging psychological questions. A large and continually growing body of research has explored the crime of homicide, its epidemiology, victims and perpetrators. The area is developing rapidly, opening up new avenues of study. The paper aims to discuss these issues.

This special issue of the Journal of Criminal Psychology brings together an exciting array of papers on homicidal behaviour, examining a wide range of issues including juvenile homicide perpetrators, school shootings, child homicide, homicide-suicide and differences in offence behaviours and victim characteristics between hard-to-solve one-off homicides and serial homicides.

The range of papers included in this special edition cover a wide range of aspects of homicidal behaviour, reflecting the importance of – and the need for – applied research moving away from examining general homicide to specialised research focusing on subtypes of homicide and subgroups of homicide offenders. A research agenda is proposed.

This editorial gives an introduction to the themes explored in this special issue and provides an overview of the selected papers.

While behaviour sequence analysis (BSA) is popular, it is not without limitations, namely, the level of detail required and time taken to run analyses; therefore, this paper aims to outline a novel method, using 30 serial homicide cases as a worked example.

Temporal analysis methods are becoming increasingly popular in applied forensic and criminological research. In recent years, BSA has become a widely used approach.

Waypoint sequencing provides a streamlined version of the traditional BSA approach, allowing for fewer behaviours to be included and providing a clearer overview of the main behaviours of interest.

Waypoint sequencing is shown in the current paper through serial killer research to show how to conduct the analyses and how it is effective in current investigations by expediting the process and allowing quicker analysis to facilitate current investigations.

The current research provides a novel approach to sequence analysis that is more useful in applied settings as it requires fewer behaviours or events than traditional BSA.

Homicide is the most severe form of crime and one that imposes the greatest societal costs. The purpose of this paper is to introduce the homicide circumplex, a set of traits, behaviors, psychological and psychiatric features that are associated with greater homicidal ideation, homicidal social cognitive biases, homicide offending and victimization, and psychopathology that is facilitative of homicide.

Using the data from a near population of federal supervised release offenders from the Midwestern USA, ANOVA, multinomial logistic, Poisson and negative binomial regression models were developed.

Greater homicidal ideation is associated with homicide offending, attempted homicide offending and attempted homicide victimization and predicted by gang activity, alias usage, antisocial personality disorder and intermittent explosive disorder. These behavioral disorders, more extensive criminal careers, African American status and gang activity also exhibited significant associations with dimensions of the homicide circumplex.

Developing behavioral profiles of offenders that exhibit homicidal ideation and behaviors are critical for identifying clients at greatest risk for lethal violence. The homicide circumplex is an innovation toward the goal that requires additional empirical validation.

Sexual sadism is a well-known risk factor for severe forms of sexual violence including sexual homicide and serial sexual homicide. The research is decidedly mixed about the association between sexual sadism and other, nonsexual forms of criminal conduct. The paper aims to discuss these issues.

Drawing on data from a census of 225 federal sex offenders from a jurisdiction in the Midwestern USA, the current study examined whether sexual sadism had a spillover effect into nonsexual crimes using correlation, ANOVA, and negative binomial regression models.

Sexual sadism was strongly associated with diverse forms of nonsexual criminal behavior, and sexual sadists had more extensive and versatile criminal careers than sex offenders without a formal diagnosis.

Practitioners should be aware of sexual sadism as a criminogenic risk factor. Sexual sadism is associated with sexual deviance and sexual violence. Sexual sadism also has spillover effects where it is associated with nonsexual offending.

Sexual sadism can be a useful risk factor for other forms of crime and recidivism and has broad application in applied correctional and research settings.

Although typologies of violence have become more common, relatively little attention has been given to Donald Black’s (1983) distinction between moralistic and predatory violence. Moralistic violence is rooted in conflict; predatory violence is rooted in exploitation. We elaborate Black’s typology and show how it is similar to, but distinct from, other typologies of violence. We also address the criteria by which typologies of any kind might be judged. Borrowing from the literatures on typologies and on standards of scientific theory, we argue that explanatory typologies should be evaluated according to four criteria: the degree to which they are powerful, theoretical, general, and parsimonious. Applying the criteria to Black’s typology, we argue that the distinction between moralistic and predatory violence is an important contribution to the arsenal of the student of violence.