Differentiating Individuals Convicted of Sexual Offenses: A Two-Country Latent Class Analysis

Sexual offenses are often part of a larger criminal career also encompassing nonsexual crimes. However, most sexual offending typologies focus on an individual's most recent sexual offense. We compare data from Belgian and Dutch national conviction cohorts and use latent class analysis to distinguish groups of individuals based on their history of sexual and nonsexual offenses, considering continuity and variety. The resulting classification is compared between individuals convicted of sexual offenses and individuals convicted of nonsexual offenses. Results show that four latent classes can be distinguished based on continuity and variety in criminal histories of individuals convicted of sexual offenses, and that some of these classes resemble those distinguished among individuals convicted of nonsexual offenses. We find limited overlap between these latent classes and typologies based solely on the index offense. Results show marked similarities across countries. These results challenge theories of sexual offending to incorporate patterns of nonsexual offending.

Reappraising and Redirecting Research on the Victim-Offender Overlap

The strong positive association between offending and victimization, or the victim-offender overlap, has received considerable amount of research attention in recent years. Empirical research has made important strides in unpacking the sources of the phenomenon, but important questions remain unanswered. Ambiguity surrounds the utility of certain theoretical explanations for the overlap, the nature of the phenomenon, and the methodological tools used to examine its etiology. Owing to these knowledge gaps, the scientific meaning of the victim-offender overlap is unclear. Moreover, a number of potentially important theoretical arguments are rarely subject to empirical testing in this line of research. The purpose of this article is to use a narrative review methodology to provide a critical reappraisal of the theoretical, empirical, and methodological research on the victim-offender overlap and offer directions for ways forward to develop a more comprehensive understanding of the phenomenon. This review includes critical analysis of 78 academic publications, along with a table that summarizes the key findings and conclusions from 18 critical empirical studies that have contributed to our understanding of the victim-offender overlap. We offer recommendations for the continued development of theoretical and methodological tools to better understand this complex phenomenon.

Childhood Maltreatment and the Risk for Criminal Justice Involvement and Victimization Among Homeless Individuals: A Systematic Review

Homeless individuals are at higher risk of criminal justice involvement (CJI) and victimization compared to their housed counterparts. Exposure to childhood maltreatment (CM; e.g., abuse, neglect) is one of the most significant predictors of CJI and victimization among homeless populations. The aim of this systematic review was to synthesize current knowledge regarding the relationship between CM and CJI and victimization among homeless individuals. Guided by the preferred reporting items for systematic reviews and meta-analyses (PRISMA) methods, a systematic search was performed using PsycINFO, MEDLINE, Embase, Web of Science, and the Cumulative Index to Nursing and Allied Health Literature for published studies investigating the relationship between CM and CJI and victimization among homeless samples. We identified 20 studies that met the inclusion criteria. Findings showed that across the majority of studies, CM, and in particular childhood physical (CPA) and sexual (CSA) abuse, is associated with increased risk of both CJI and victimization, regardless of various important factors (e.g., sociodemographic characteristics, psychiatric disorders, substance use). These findings support the need for prevention and treatment for "families at risk" (i.e., for intimate partner violence, child abuse and neglect) and also document the need for trauma-informed approaches within services for homeless individuals. Future research should focus on prospective designs that examine victimization and CJI in the same samples.

Showup identification decisions for multiple perpetrator crimes: Testing for sequential dependencies

Research in perception and recognition demonstrates that a current decision (i) can be influenced by previous ones (i–j), meaning that subsequent responses are not always independent. Experiments 1 and 2 tested whether initial showup identification decisions impact choosing behavior for subsequent showup identification responses. Participants watched a mock crime film involving three perpetrators and later made three showup identification decisions, one showup for each perpetrator. Across both experiments, evidence for sequential dependencies for choosing behavior was not consistently predictable. In Experiment 1, responses on the third, target-present showup assimilated towards previous choosing. In Experiment 2, responses on the second showup contrasted previous choosing regardless of target-presence. Experiment 3 examined whether differences in number of test trials in the eyewitness (vs. basic recognition) paradigm could account for the absence of hypothesized ability to predict patterns of sequential dependencies in Experiments 1 and 2. Sequential dependencies were detected in recognition decisions over many trials, including recognition for faces: the probability of a yes response on the current trial increased if the previous response was also yes (vs. no). However, choosing behavior on previous trials did not predict individual recognition decisions on the current trial. Thus, while sequential dependencies did arise to some extent, results suggest that the integrity of identification and recognition decisions are not likely to be impacted by making multiple decisions in a row.

The scaling of crime concentration in cities

Crime is a major threat to society’s well-being but lacks a statistical characterization that could lead to uncovering some of its underlying mechanisms. Evidence of nonlinear scaling of urban indicators in cities, such as wages and serious crime, has motivated the understanding of cities as complex systems—a perspective that offers insights into resources limits and sustainability, but that usually neglects details of the indicators themselves. Notably, since the nineteenth century, criminal activities have been known to occur unevenly within a city; crime concentrates in such way that most of the offenses take place in few regions of the city. Though confirmed by different studies, this concentration lacks broad analyses on its characteristics, which hinders not only the comprehension of crime dynamics but also the proposal of sounding counter-measures. Here, we developed a framework to characterize crime concentration which divides cities into regions with the same population size. We used disaggregated criminal data from 25 locations in the U.S. and the U.K., spanning from 2 to 15 years of longitudinal data. Our results confirmed that crime concentrates regardless of city and revealed that the level of concentration does not scale with city size. We found that the distribution of crime in a city can be approximated by a power-law distribution with exponent α that depends on the type of crime. In particular, our results showed that thefts tend to concentrate more than robberies, and robberies more than burglaries. Though criminal activities present regularities of concentration, we found that criminal ranks have the tendency to change continuously over time—features that support the perspective of crime as a complex system and demand analyses and evolving urban policies covering the city as a whole.

Investigator Sensitivity to Alibi Witness Inconsistency after a Long Delay

In two studies, mock investigators conducted a computer-based investigation of a crime involving an alibi witness who varied in the consistency of his statements taken 5 years apart. Investigators showed evidence of skepticism of alibi witness statements in which major contradictions (activity, location) were present, and some skepticism of statements in which minor (activity) details were contradictory. Entirely consistent statements were judged favorably, and reduced perceptions of suspect guilt (Study 2). The age of the alibi witness did not impact judgments of suspect guilt when children (6 years) and adults (25 years) were compared (Study 1, N = 254), or when children of different ages were compared (6, 8, 11 years; Study 2, N = 234). The present data suggest that investigators were relatively more sensitive to considerations of accuracy than honesty. Copyright © 2017 John Wiley & Sons, Ltd.

Positive criminology in practice

The discourse regarding offender rehabilitation has been criticized by various scholars who have claimed that reducing negative causes and managing risk will not automatically prompt positive human development and elements that are associated with desistance. Positive criminology is an innovative concept that challenges the common preoccupation with negative elements, by placing emphasis on human encounters and forces of inclusion that are experienced positively by target individuals and that can promote crime desistance. However, as the concept is relatively new, there are still no guiding principles for the practice of positive criminology that could direct research and the criminal justice system. This article attempts to fill that gap by providing principles that could be practiced by criminal justice personnel and examples of different interventions that reflect positive criminology. The article also provides ideological explanations for adopting the concept of positive criminology in practice.

[Ideal type and history--a critical review of applied criminology]

Applied Criminology describes an established criminological school in the German-speaking area, which was founded by Hans Göppinger and Michael Bock, criminologists at Tübingen, in the 1980s and has meanwhile published a number of comprehensive basic methodological papers. The conceptual centrepiece with interdisciplinary approach is the formation and application of concepts referring to the so-called ideal type, which has been essentially inspired by the epistemology of Max Weber. However, the result of a critical reconstruction of these fundamentals is that the claimed interdisciplinary approach comes into conflict with a second much more phenomenological approach of Applied Criminology which is unable to comply with the political implications of criminological research and thus disavows the necessary historical relationality of the ideal type concepts.

Nonresponse bias in randomized controlled experiments in criminology: Putting the Queensland Community Engagement Trial (QCET) under a microscope

OBJECTIVES

The goal of this article is to examine whether or not the results of the Queensland Community Engagement Trial (QCET)-a randomized controlled trial that tested the impact of procedural justice policing on citizen attitudes toward police-were affected by different types of nonresponse bias.

METHOD

We use two methods (Cochrane and Elffers methods) to explore nonresponse bias: First, we assess the impact of the low response rate by examining the effects of nonresponse group differences between the experimental and control conditions and pooled variance under different scenarios. Second, we assess the degree to which item response rates are influenced by the control and experimental conditions.

RESULTS

Our analysis of the QCET data suggests that our substantive findings are not influenced by the low response rate in the trial. The results are robust even under extreme conditions, and statistical significance of the results would only be compromised in cases where the pooled variance was much larger for the nonresponse group and the difference between experimental and control conditions was greatly diminished. We also find that there were no biases in the item response rates across the experimental and control conditions.

CONCLUSION

RCTs that involve field survey responses-like QCET-are potentially compromised by low response rates and how item response rates might be influenced by the control or experimental conditions. Our results show that the QCET results were not sensitive to the overall low response rate across the experimental and control conditions and the item response rates were not significantly different across the experimental and control groups. Overall, our analysis suggests that the results of QCET are robust and any biases in the survey responses do not significantly influence the main experimental findings.

Understanding gender bias in face recognition: effects of divided attention at encoding

Prior research has demonstrated a female own-gender bias in face recognition, with females better at recognizing female faces than male faces. We explored the basis for this effect by examining the effect of divided attention during encoding on females' and males' recognition of female and male faces. For female participants, divided attention impaired recognition performance for female faces to a greater extent than male faces in a face recognition paradigm (Study 1; N=113) and an eyewitness identification paradigm (Study 2; N=502). Analysis of remember-know judgments (Study 2) indicated that divided attention at encoding selectively reduced female participants' recollection of female faces at test. For male participants, divided attention selectively reduced recognition performance (and recollection) for male stimuli in Study 2, but had similar effects on recognition of male and female faces in Study 1. Overall, the results suggest that attention at encoding contributes to the female own-gender bias by facilitating the later recollection of female faces.

A different perspective: introducing positive criminology

Positive criminology is a new conceptual perspective of criminology, encompassing several theories and models. Positive criminology refers to a focus on individuals' encounters with forces and influences that are experienced as positive, which distance them from deviance and crime, whether by means of formal and informal therapy programs and interventions, such as self-help groups; through emphasis of positive social elements, such as exposure to goodness, social acceptance, and reintegrative shaming; or based on positive personal traits, such as resilience and coherence. The perspective of positive criminology broadens that of traditional criminology, which focuses mainly on understanding the factors and processes that lead individuals and groups to what is defined as deviant and criminal behavior. Positive criminology is implemented in treatment and rehabilitation of individuals and groups that have demonstrated deviant and criminal behavior, by emphasizing positive experiences that may potentially prevent or discourage continued criminal behavior. Positive criminology is also expressed in prevention based on a positive approach.

Criminological research in contemporary China: challenges and lessons learned from a large-scale criminal victimization survey

This article discusses research experience gained from a large-scale survey of criminal victimization recently conducted in Tianjin, China. The authors review some of the more important challenges that arose in the research, their responses to these challenges, and lessons learned that might be beneficial to other scholars who are interested in conducting criminological research in China. Their experience underscores the importance of understanding the Chinese political, cultural, and academic context, and the utility of collaborating with experienced and knowledgeable colleagues "on site." Although there are some special difficulties and barriers, their project demonstrates the feasibility of original criminological data collection in China.

Developing comparative criminology and the case of China: an introduction

Although comparative criminology has made significant development during the past decade or so, systematic empirical research has only developed along a few topics. Comparative criminology has never occupied a central position in criminology. This article analyzes the major theoretical and methodological impediments in the development of comparative criminology. It stresses a need to shift methodology from a conventional primary approach that uses the nation as the unit of analysis to an in-depth case study method as a primary methodological approach. The article maintains that case study method can overcome the limitation of its descriptive tradition and become a promising methodological approach for comparative criminology.

Understanding the relationship between mental disorder and violence: the need for a criminological perspective

This paper offers a criminologically informed framework to guide research on the relationship between mental disorder and violence. Criminological theories examined include social learning, social stress, social control, rational choice, and social disorganization. In addition, the "criminal careers" and "local life circumstance" methodologies are reviewed. It is argued that adopting a criminologically informed framework that takes into account within-person changes over time will contribute greatly to our understanding of the factors that affect violence among people with mental disorder living in the community, and enhance the capacity of research to support effective evidenced-based case management programs aimed at reducing violence.

Survey of 1276 shoeprint impressions and development of an automatic shoeprint pattern matching facility

1276 shoeprints were collected at a scientific exhibition. Details regarding the age groups of the participants, style, size and manufacturer/brand of their shoes were recorded. The impressions were assigned to pattern groups showing that the most common pattern was present in only 1% of the population studied and most patterns were much less common. The impressions were digitized and a system developed for automatically sorting a database of images of outsole patterns in response to a reference image. The database images are ranked so that those from the same pattern group as the reference shoeprint are likely to be at the start of the list. A database of 486 complete shoeprint images belonging to 142 pattern groups was established with each group containing two or more examples. Tests of the system have shown that the first-ranked database image belongs to the same pattern group as the reference image 60% of the time and that a correct match appears within the first 5% of the ranked images 88% of the time. The system has translational and rotational invariance so that the spatial positioning of the reference shoeprint images does not have to correspond with the spatial positioning of the shoeprint images of the database. The performance of the system for matching partial shoeprints was also determined.

An extended likelihood ratio framework for interpreting evidence

This paper reviews some current methods, the likelihood ratio-based approach and the full Bayesian approach for the interpretation of evidence and discusses previously identified shortcomings in them. It suggests an approach based on a compromise--based on an extended likelihood ratio--that may combine the merits of logic without overstepping acceptable bounds for the forensic scientist in the presentation of evidence. The approach is exposed formally and takes advantage of inferential networks called Bayesian networks.

Forensic DNA identification of animal-derived trace evidence: tools for linking victims and suspects

AIM

To evaluate the population substructure of purebred dogs and cats in order to estimate the true significance of a microsatellite-based DNA match for use as evidence in legal proceedings. The high frequency of animal hair as a forensic evidence submission necessitates the development of mitochondrial analysis tools as well.

METHODS

Random samples from a large convenience collection of veterinary diagnostic submissions from the western USA were used, as well as contributed samples of unrelated purebred cats and dogs. Dogs (n=558) were profiled with 17 microsatellites and the data evaluated for Hardy Weinberg and linkage equilibrium. The mitochondrial control region (D loop) of dogs (n=348) and cats (n=167) was sequenced to determine the haplotype distribution.

RESULTS

Domestic dogs in the western United States showed significant population substructure with marked associations within loci but no disequilibrium between loci. A population substructure coefficient Theta=0.11 is recommended for calculating genotype frequencies. Mitochondrial haplotypes in cats and dogs show less variation than human haplotypes.

CONCLUSION

Although population substructure occurs in domestic dogs (and can be inferred in cats), the discriminatory power of microsatellite analysis is dramatic with even partial DNA types, strongly supporting the prosecution of perpetrators in five discussed cases. Mitochondrial analysis, while less powerful, adds a layer of evidence in four discussed cases.

[Multiple homicides--forensic and criminologic aspects]

The interpretation of medicolegal findings in homicide is an important tool of case profiling (so-called "operative case analysis"). In 17 cases of "multiple homicides" involving 22 offenders (21 males, 1 female; mean age 33 years) and 45 victims (21 males, 24 females; mean age 35 years; 41 fatalities, 4 survivors), the autopsy reports and the prosecution authorities' files were retrospectively analysed with regard to individual characteristics of perpetrators and victims, circumstances, and mode of commitment in order to comprehensively characterise relevant forensic and criminologic aspects. 31 victims were found to belong to the close social environment of the perpetrator, and 32 killings were committed in the victim's, perpetrator's or the joint flat. The main motives included greed (n = 7), personal conflicts (n = 5) and concealing of a crime (n = 9). The relevant injuries were attributable to gunshot wounds (n = 13), sharp force (n = 11), blunt force (n = 3), ligature strangulation (n = 3), smothering (n = 6), fire/carbon monoxide (n = 2) and combined impacts (n = 7). In 12 victims, defense injuries were found. The blood alcohol concentration exceeded 1.5 g/l in 5 victims. In 5 offenders, a psychiatric impairment of juridical responsibility was assessed (and 20 German criminal code, n = 1, psychosis; and 21 German criminal code, n = 4; acute alcohol intoxication). As far as data were available, 16 crimes were judged as murder, 12 as manslaughter and one as physical injury with fatal outcome.

Enhancing fraud prevention and detection by profiling fraud offenders

AIMS

The paper first focuses on the crime of fraud and then on approaches to profiling offenders before examining closely studies of fraud offenders and their motivation.

METHOD

Drawing on the existing empirical literature, a profile of the serious fraud offender is presented and critiqued together with a taxonomy of such offenders comprising 12 types.

CONCLUSIONS

The implications of the findings for fraud detection and prevention are discussed.

Recent developments in methods of chemical analysis in investigations of firearm-related events

A review of recent (approximately the last ten years) developments in the methods used for chemical analysis in investigations of firearm-related events is provided. This review discusses:examination of gunshot (primer) residues (GSR) and gunpowder (propellant) residues on suspects and their clothing;detection of firearm imprints on the hands of suspects;identification of the bullet entry holes and estimation of shooting distance;linking weapons and/or fired ammunition to the gunshot entries, and estimation of the time since discharge.

A graphical model for the evaluation of cross-transfer evidence in DNA profiles

The role of graphical models in the assessment of transfer evidence is described with particular reference to the role of cross-transfer evidence. The issues involved in the determination of factors (nodes), associations (links) and probabilities to be included are discussed. Four types of subjective probabilities are of particular interest: those for transfer, persistence and recovery; innocent acquisition; relevance; innocent presence. Examples are given to illustrate the roles of various aspects of the suspect's and victim's lifestyle and the investigation of the evidence found on the suspect and victim in assessing the probability of ultimate issue, that the suspect committed the crime.

Cold Case Homicides Investigative Interviews of Child Witnesses

Nurses interviewing child witnesses in cold case homicide investigations face unique challenges arising from the passage of time. 2. Postevent influences must be evaluated carefully when examining children's descriptions about remote events. 3. Interview strategies that incorporate various types of developmentally appropriate tasks offer highly traumatized children the opportunity to tell their stories. 4. Although years may have passed, some children are able to provide accurate and unique details about a homicide they witnessed.

Fluvial transport of human remains in the lower Mississippi River

The Mississippi River has claimed many lives over the last several decades. A better understanding of the universal dynamics of its fluvial system can help direct the production of a predictive model regarding the transportation of human remains in the river. The model may then be applied to situations where the location and the identification of water victims are necessarily part of the recovery process. Results from the preliminary phase of a longitudinal project involving the transport of human remains in the Mississippi River are presented and represent the analyses of 233 case files of river victims. A provisional model for fluvial transport of human remains in the Mississippi River is proposed and examined. This model indicates that time in the river and distance a body travels are related. Such a model may assist in pinpointing entry location for unidentified human remains found in the river or on its banks. Further, it has the potential to provide local and regional law enforcement agencies, the United States Coast Guard, and other search and rescue organizations with primary search areas when someone is missing in the river. Other results from this study indicate that a relationship exists between the side of the river where victims enter the water and the side of the river where the remains are recovered. Finally, relationships are established between the length of time before recovery of the remains and state of preservation exhibited by those remains. A secondary benefit from this study is a database of river victims that can be used by a variety of different agencies.

Trace DNA: a review, discussion of theory, and application of the transfer of trace quantities of DNA through skin contact

Advances in STR PCR DNA profiling technology allow for the analysis of minute quantities of DNA. It is frequently possible to obtain successful DNA results from cellular material transferred from the skin of an individual who has simply touched an object. Handling objects, such as weapons or other items associated with a crime, touching surfaces, or wearing clothing, may represent sufficient contact to transfer small numbers of DNA bearing cells, or trace DNA, which can be successfully analyzed. With this minimal amount of contact required to yield a suspect profile comes tremendous crime solving potential, and a number of considerations for prudent application, and the maximization of evidentiary value. Evidentiary materials not previously considered must be recognized and preserved, and the resulting DNA type profiles interpreted in their proper forensic context.

Interpreting small quantities of DNA: the hierarchy of propositions and the use of Bayesian networks

The dramatic increase in the sensitivity of DNA profiling systems that has occurred over recent years has led to the need to address a wider range of interpretational problems in forensic science. The issues surrounding questions of the kind "whose DNA is this?" have been the subject of considerable controversy but now it is clear that the emphasis is shifting to questions of the kind "how did this DNA get here?" Such issues are discussed in this paper and new insights are provided by two particular recent developments. First, the notion of the "hierarchy of propositions" that has arisen from a project called Case Assessment and Interpretation (CAI) that has been running in the British Forensic Science Service (FSS). Second, a technique for drawing inferences in the face of many interacting considerations, known as "Bayesian networks"--or "Bayes' nets" for short--that has been the subject of an earlier paper in this journal (1). The discussion is carried out by means of case studies, based on actual cases. It is clear that, whereas the inference in relation to the source of the DNA in a crime sample might be overwhelmingly strong, the inference in relation to the propositions that a jury must consider relating to the identity of the actual offender may be much more tentative.

Forensic comparison of soils by bacterial community DNA profiling

This preliminary investigation has shown that a soil microbial community DNA profile can be obtained from the small sample of soil recovered from the sole of a shoe, and from soil stains on clothing. We have also shown that these profiles are representative of the site of collection and therefore could potentially be used as associative evidence to prove a link between suspects and crime scenes. Soil community profiles were obtained using the T-RFLP fingerprinting method that uses fluorescent primer technology and semi-automated analysis techniques similar to those used in human DNA profiling in forensic laboratories.

Development of fluorescent markers using polycyclic aromatic hydrocarbons with vaseline

Identifiable fluorescent markers were developed as tracers to tail suspects using phenanthrene, anthracene, fluoranthene, pyrene, perylene, and coronene in vaseline. Vaseline was used as a carrier of the marker. Of the six compounds in the vaseline, perylene and fluoranthene were readily observed under ultraviolet (UV) light at a wavelength of 365 nm. All six compounds were identified selectively and sensitively without interference of vaseline using a high performance liquid chromatograph (HPLC) with a fluorescence detector. The detection limit was much less than 1 ng, corresponding to that of the observation behavior under UV light. The results showed that each component with vaseline was more effective than the individual component for the delay in degradation. The case examples of the fluorescent markers are shown.

Seeing through the face of deception

We have developed a high-definition thermal-imaging technique that can detect attempted deceit by recording the thermal patterns from people's faces. This technique has an accuracy comparable to that of polygraph examination by experts and has potential for application in remote and rapid security screening, without the need for skilled staff or physical contact.

Predicting the home location of serial offenders: a preliminary comparison of the accuracy of human judges with a geographic profiling system

The accuracy with which human judges, before and after 'training', could predict the likely home location of serial offenders was compared with predictions produced by a geographic profiling system known as Dragnet. All predictions were derived from ten spatial displays, one for each of ten different U.S. serial murderers, indicating five crime locations. In all conditions participants were asked to place an 'X' on each spatial display corresponding to where they thought the offender lived. In the control condition, a comparison was made between the accuracy of these predictions for 21 participants on two separate occasions a few minutes apart. In the experimental condition, between their first and second predictions the 21 participants were given two heuristics to follow--distance-decay and circle hypothesis. Results showed that participants with no previous knowledge of geographic profiling were able to use the two heuristics to improve the accuracy of their predictions. The overall accuracy of the second set of predictions for the experimental group was also not significantly different from the accuracy of predictions generated by Dragnet.

Fingerprints classification using artificial neural networks: a combined structural and statistical approach

This paper describes a fingerprint classification algorithm using Artificial Neural Networks (ANN). Fingerprints are classified into six categories: arches, tented arches, left loops, right loops, whorls and twin loops. The algorithm extracts a string of symbols using the block directional image of a fingerprint, which represents the set of structural features for this image. The moment representing the statistical feature of the pattern is computed for this string and its Euclidean Distance Measures (EDM) are computed by using this moment. Our discrimination system uses a multilayer artificial neural network composed of six subnetworks one for each class. The classifier was tested on 1,500 images of good quality in the Egyptian Fingerprints database; images with poor quality were rejected. In the six-class problem the network achieved 95% classification accuracy. In the five-class problem when we place whorls and twin loops together in the same category the classification accuracy was around 99%. In the four-class problem when we place arches and tented arches in the same class the classification accuracy was 99%.

Pollen on grass clippings: putting the suspect at the scene of the crime

In a case of alleged sexual assault, the pollen content of samples of grass clippings and soil from the suspect's clothing and shoes was compared to that of a sample of grass clippings from the alleged crime scene (a grassy area) to determine whether or not the suspect had been at the scene. The clothing and shoe samples showed a very strong correlation with each other and with the sample from the alleged crime scene in the combination of the different types of pollen present, very strongly supporting the contention that the suspect had been at the scene.

Comparison of PowerPlex 16, PowerPlex1.1/2.1, and ABI AmpfISTR Profiler Plus/COfiler for forensic use

AIM

Several amplification and detection formats for the analysis of short tandem repeat loci are readily available to the forensic laboratory. Careful consideration must be given to the throughput, sensitivity, concordance, data interpretation, facility requirements, and costs of operation. The Pennsylvania State Police DNA Laboratory sought to establish that of any of the amplification or detection formats generally used in the United States generates concordant results and that the use of several formats within one laboratory provides a solution to the interpretation of difficult evidentiary samples.

METHODS

Validation work consisting of sensitivity, precision, mixture, and substrate studies was performed by use of each of three detection formats (ABI Prism(r)310 Genetic Analyzer, ABI Prism(r)377 DNA Sequencer, and the Hitachi FMBIO(r)II Fluorescent Scanner) and three amplification systems (GenePrint(r) PowerPlex 16, GenePrint(r) PowerPlex 1.1/2.1, and AmpflSTR ProfilerPlus/COfiler). The results generated in each of the formats were compared, along with the problems incurred.

RESULTS

All allele calls were concordant, with the exception of primer region variants, and all detection systems were sensitive and reliable. Even with the use of multiple formats, a general protocol can be written with only one set of interpretation guidelines.

CONCLUSION

National databases can be used with input data from any of these formats. The use of several detection formats allowed the forensic scientist to select a system, based on sample quality, quantity, and throughput requirements. Interpretation issues resulting from complex mixtures, degraded samples, rare microvariants, internal primer variants, unusual heterozygote ratios, above or below ladder alleles, and potential tri-alleles can be verified.

Introduction to forensic science

Modern day criminal investigation has reached a point of sophistication requiring the involvement of many different disciplines to solve a crime. Each discipline inserts a part of the puzzle until it is complete. It is important to understand what each forensic expert has to offer. The coroner or medical examiner, asking for input from the various experts until enough information is received to determine the cause and manner of death, is usually the keystone to a death investigation. This information is then shared with the police investigators and prosecutor. This calls for the utmost cooperation and communication among those involved.

New tools. A new breed of high-tech detectives

Forensic scientists are equipping police investigators with powerful tools for collecting and analyzing evidence. But as detection techniques become increasingly sensitive, the problem of sifting the wheat from the chaff at a crime scene mushrooms, guaranteeing a role for the human investigator despite all the gadgetry. Moreover, some developments are also raising civil liberties concerns.

Solid-phase extraction for profiling of ecstasy tablets

A solid-phase extraction (SPE) procedure has been developed for impurity profiling of illicit tablets containing 3,4-methylenedioxy-N-methyl-amphetamine (MDMA, ecstasy). Following initial comparison of liquid-liquid extraction and solid-phase extraction, SPE was found to be preferable because it afforded higher extraction efficiencies and shorter extraction times. Procedure blank samples were also analyzed to identify constituents of the extracts which did not originate in the ecstasy tablets. The developed procedure was subsequently applied to 12 samples of seized ecstasy tablets and a comparison was made of these samples to determine similarities and obtain inferences with respect to commonality of origin.

Analysis of primer residue from lead free ammunition by X-ray microfluorescence

In forensic science, the analysis of gunshot residues was traditionally done by the detection of lead (Pb), antimony (Sb) and barium (Ba) usually found in a primer. However, the recent development of lead-free ammunition represents a new challenge for ballistic specialists. This analysis study gunshot residues from primers and ammunitions in the area surrounding bullet holes, a very important tool to determine the shooting distance. The ammunitions used were 9 mm Luger and .38 spl + p calibers, where lead in the primer was replaced with strontium (Sr) and where the lead bullet was plated with copper (Total Metal Jacket). Gunshot analysis results were obtained using an energy dispersive X-ray microfluorescence spectrometer. The method allows the detection and quantification of strontium residues on the target up to a distance of 45 cm.

Physical and chemical evidence remaining after the explosion of large improvised bombs. Part 1: firings of ammonium nitrate/sugar and urea nitrate

Recent criminal acts in the United Kingdom, United States and other countries have demonstrated the dangers to public safety from the criminal use of improvised explosives on a large scale. Four sets of trials were carried out over four years, partly in collaboration with the United States Federal Bureau of Investigation, involving the firing of large bombs, mostly fertilizer based. The principal objectives of the firings were to measure the physical effects of the explosions upon objects representative of those that would be found at a real bomb scene and to recover any chemical traces deposited on these objects. The results are intended for use as an aid in determining the approximate size and type of an explosive employed in a terrorist attack. This paper describes the background behind the trials, the procedures for preparation of witness materials and charges, and the collection and analysis of physical and chemical evidence.

The detection and analysis of ignitable liquid residues extracted from human skin using SPME/GC

A simple, fast, inexpensive, and sensitive technique for the detection and identification of flammable or combustible liquid residues on the skin of arson suspects is presented. The use of solid phase microextraction (SPME) for the analysis of ignitable liquid residues has been demonstrated and it is shown in this work that this technique is effective in extracting these liquid residues at extremely low quantities. Microliter quantities of controlled spikes of gasoline, diesel fuel, and charcoal lighter fluid were deposited on the hands of a volunteer and extracted after several time intervals. The SPME technique can recover very small amounts of liquid deposits on skin up to 3.5 h after exposure, depending on the class of the ignitable liquid residue used.

Physical and chemical evidence remaining after the explosion of large improvised bombs. Part 2: Firings of calcium ammonium nitrate/sugar mixtures

Six test firings of large improvised explosive devices were carried out. The principal objectives of the firings were to measure the physical effects of the explosions upon representative objects placed nearby and to recover any chemical traces deposited on these objects. The results are intended for use as an aid in determining the approximate size and type of an explosive employed in terrorist attacks. Three 454 kg charges of a mixture of calcium ammonium nitrate (CAN) fertilizer and sugar, and three 2268 kg charges of a similar mixture, all confined in cylindrical steel containers were fired. Each charge was surrounded by 19 road signs mounted on posts and four vehicles, to act as witness materials. The analysis of aqueous swab extracts taken from the witness materials after firing showed the recovery of nitrate, ammonium and low levels of glucose. No sucrose was detected. Nitrate was usually recovered in greater quantities than ammonium and recovery generally decreased with increasing distance from the charges in any given direction. Quantities recovered from objects placed at the same distance in different directions varied considerably. Patterns of physical damage to the witness materials could be discerned according to their distance from the charge and the size of the charge. The velocities of detonation and air blast effects were measured.