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Forensic scientists routinely use DNA for identification and to match samples with individuals. Although standard approaches are effective on a wide variety of samples in various conditions, issues such as low-template DNA samples and mixtures of DNA from multiple individuals pose significant challenges. Extreme examples of these challenges can be found in the field of ancient DNA, where DNA recovered from ancient remains is highly fragmented and marked by patterns of DNA-damage. Additionally, ancient libraries are often characterized by low endogenous DNA content and contaminating DNA from outside sources. As a result, standard forensics approaches, such as amplification of short-tandem repeats, are not effective on ancient samples. Alternatively, ancient DNA is routinely directly sequenced using high-throughput sequencing to survey the molecules that are present within a library. However, the resulting sequences are not easily compared for the purposes of identification, as each data set represents a random and, in some cases, non-overlapping, sample of the genome.In this dissertation, I present two approaches for interpreting shotgun sequences that address two common issues in forensic and ancient DNA: extremely low nuclear genome coverage and mixtures of sequences from multiple individuals. First, I present an approach to test for a common source individual between extremely low-coverage sequence data sets that makes use of the vast number of single-nucleotide polymorphisms (SNPs) discovered by surveys of human genetic diversity. As almost no observed SNP positions will be common to both samples, our method uses patterns of linkage disequilibrium as modeled by a panel of haplotypes to determine whether observations made across samples are consistent with originating from a single individual. I demonstrate the power of this approach using coalescent simulations, downsampled high-throughput sequencing data and published ancient DNA data. Second, I present an approach for interpreting mixtures of mitochondrial DNA sequences from multiple individuals. Mixed DNA samples are common in forensics investigations, either from the direct nature of a case (e.g., a sample containing DNA from both a victim and a perpetrator) or from outside contamination. I describe an expectation maximization approach for detecting the mitochondrial haplogroups contributing to a mixture and partitioning fragments by haplogroup to reconstruct the underlying haplotypes. I demonstrate the approach’s feasibility, accuracy, and sensitivity on both in silico and in vitro sequence mixtures. Finally, I present the results of applying our mixture interpretation approach on ancient contact DNA recovered from ~700 year old moccasin and cordage samples.

Background Every year, millions of children face sexual exploitation worldwide. In India, 109 children (National Crime Records Bureau2018) were sexually abused everyday (22% jump from the previous year). Even with advanced DNA techniques, the conviction rate remains low. The methods used for forensic DNA evidence analysis vary around the world, but the primary step of biological evidence collection plays the most vital role. Proper and timely evidence collection from the victim by a trained medical professional is important. Main body Dynamics of child sexual assault being massively different from an adult rape demands altogether different approach of evidence collection. A standard sexual kit employed for evidence collection needs urgent modifications considering genital development of pre- and post-pubertal victims. In the present study, parameters including systemic collection and evaluation of forensic evidences, medico-legal examination, and developmental consequences of sexual assault on pre-pubertal victims were assessed. Further suggestions for separate evidence collection kit during medico-legal examination were given for pre-pubertal victims and alleged accused in sexual assault cases in order to streamline and for better evaluation of DNA analysis in forensic laboratories. Conclusion The importance of expert medical practitioners plays a significant role in collection of appropriate information and evidences from the victim of sexual assault. General guidelines for evidence collection in sexual assault cases are not well suited for pre-pubertal victims. Appropriate reforms pertaining to the age and genital development of victims are required. Securing clothing as forensic evidence is essential in most cases as it turned out to be the exclusive evidence bearing material. The purpose of this article is to bring awareness about the thorough medical examination and modified sexual assault kit for pre-pubertal victims and alleged accused for a better approach in evidence collection and conviction rate.

The FORensic Capture Enrichment (FORCE) panel is an all-in-one SNP panel for forensic applications. This panel of 5,422 markers encompasses common, forensically relevant SNPs (identity, ancestry, phenotype, X- and Y-chromosomal SNPs), a novel set of 3,931 autosomal SNPs for extended kinship analysis, and no clinically relevant/disease markers. The FORCE panel was developed as a custom hybridization capture assay utilizing ∼20,000 baits to target the selected SNPs. Five non-probative, previously identified World War II (WWII) cases were used to assess the kinship panel. Each case included one bone sample and associated family reference DNA samples. Additionally, seven reference quality samples, two 200-year-old bone samples, and four control DNAs were processed for kit performance and concordance assessments. SNP recovery after capture resulted in a mean of ∼99% SNPs exceeding 10X coverage for reference and control samples, and 44.4% SNPs for bone samples. The WWII case results showed that the FORCE panel could predict 1st to 5th degree relationships with strong statistical support (likelihood ratios over 10,000 and posterior probabilities over 99.99%). To conclude, SNPs will be important for further advances in forensic DNA analysis. The FORCE panel shows promising results and demonstrates the utility of a 5,000 SNP panel for forensic applications.

DNA analyses from challenging samples such as touch evidence, hairs and skeletal remains push the limits of the current forensic DNA typing technologies. Reverse complement PCR (RC-PCR) is a novel, single-step PCR target enrichment method adapted to amplify degraded DNA. The sample preparation process involves a limited number of steps, decreasing the labor required for library preparation and reducing the possibility of contamination due to less sample manipulation. These features of the RC-PCR make the technology a unique application to successfully target single nucleotide polymorphisms (SNPs) in fragmented and low copy number DNA and yield results from samples in which no or limited data are obtained with standard DNA typing methods. The developed RC-PCR short amplicon 85 SNP-plex panel is a substantial improvement over the previously reported 27-plex RC-PCR multiplex that will provide higher discrimination power for challenging DNA sample analyses.

Forensic DNA phenotyping (FDP) encompasses a set of technologies aimed at predicting phenotypic characteristics from genotypes. Advocates of FDP present it as the future of forensics, with an ultimate goal of producing complete, individualised facial composites based on DNA. With a focus on individuals and promised advances in technology comes the assumption that modern methods are steadily moving away from racial science. Yet in the quantification of physical differences, FDP builds upon some nineteenth- and twentieth-century scientific practices that measured and categorised human variation in terms of race. In this article I complicate the linear temporal approach to scientific progress by building on the notion of the folded object. Drawing on ethnographic fieldwork conducted in various genetic laboratories, I show how nineteenth- and early twentieth-century anthropological measuring and data-collection practices and statistical averaging techniques are folded into the ordering of measurements of skin color data taken with a spectrophotometer, the analysis of facial shape based on computational landmarks and the collection of iris photographs. Attending to the historicity of FDP facial renderings, I bring into focus how race comes about as a consequence of temporal folds.

Single-cell sequencing is a fast developing and very promising field, however, it is not commonly used in forensics. The main motivation behind introducing this technology into forensics is to improve mixture deconvolution, especially when a trace consists of the same cell type. Successful studies demonstrate the ability to analyze a mixture by separating single cells and obtaining CE-based STR profiles. This indicates a potential use of the method in other forensic investigations, like forensic DNA phenotyping, in which using mixed traces is not fully recommended. For this study, we collected single-source autopsy blood from which the white cells were first stained and later separated with the DEPArray™ N×T System. Groups of 20, 10, and 5 cells, as well as 20 single cells, were collected and submitted for DNA extraction. Libraries were prepared using the Ion AmpliSeq™ PhenoTrivium Panel, which includes both phenotype (HIrisPlex-S: eye, hair, and skin color) and ancestry-associated SNP-markers. Prior to sequencing, half of the single-cell-based libraries were additionally amplified and purified in order to improve the library concentrations. Ancestry and phenotype analysis resulted in nearly full consensus profiles resulting in correct predictions not only for the cells groups but also for the ten re-amplified single-cell libraries. Our results suggest that sequencing of single cells can be a promising tool used to deconvolute mixed traces submitted for forensic DNA phenotyping.

In the current scenario, DNA typing is the need of forensic science field due to its ability to provide results in much shorter time. In view of advancement of forensic DNA typing and incensement in the number of STRs markers, Promega offered a new VersaPlex™ 27PY system with 27 loci (23 autosomal STR loci, Amelogenin, DYS391 and two rapidly mutating Y-STR loci (DYS570 and DYS576)). In this study, the efficacy of “23 autosomal STR loci” for paternity testing and personal identification was demonstrated in Indian population. For this, 217 central Indians were tested and all the statistical parameters of forensic and population genetic interest were calculated. In addition, sensitivity of the kit was also tested for forensic casework. During investigation with VersaPlex™ 27PY system, allele 11 at locus TPOX was observed to be most frequent with the highest allelic frequency 0.432. Studied 23 loci showed valuable together with highest value of combined power of discrimination (CPD = 1), combined power of exclusion (CPI = 0.9999999989) and lowest value of combined matching probability (CPM = 7.92x10-28).

The analysis of forensic DNA profiles is complicated by the presence of undesirable artefactual peaks such as stutter, pull-up, and dye blobs. We describe the developmental validation of FaSTR™ DNA analysis software, which can assist with the streamlined analysis of forensic DNA profiles. A total of 3403 single-source and mixed DNA profiles generated using seven different STR profiling kits were analysed in FaSTR™ DNA. Results were compared with outputs from GeneMapper™ ID-X analysis software. Over 99.95% of peak designations were concordant, corresponding to over 232,000 peaks. There were no significant differences found in peak size however differences in peak height were observed between the software programmes. Peaks greater than 1000 rfu were generally taller in GeneMapper™ ID-X than in FaSTR™ DNA. At lower peak heights, peaks were often taller in FaSTR™ DNA, due to differences in how each software applies baseline correction to the electropherogram. Allele-specific stutter filters in FaSTR™ DNA correctly designated 99.3% of stutter peaks analysed (5174 peaks comprising four stutter types) in 265 single-source GlobalFiler™ profiles. FaSTR™ DNA was shown to be effective for its intended use as analysis software for the designation of alleles and the identification of artefacts such as stutter, pull-up, and spikes.

This study was conducted to come up with data on Y-STR markers for the population of Rajasthan comprising of the western arid region of India. Y-STR analysis is an established tool in forensic DNA casework and ancestry research. We analyzed 23 Y-STRs in randomly selected 310 unrelated individuals living within the geographical area of Rajasthan to establish parameters of forensic interest. Out of 310 haplotypes, 309 unique haplotypes were observed, which revealed a high discrimination capacity with a value of 0.997 for the studied loci. The gene diversity (GD) and haplotype diversity (HD) for the studied 23 Y STRs were found to be 0.664 and 0.666, respectively. In the population of Rajasthan, locus DYS385a/b showed the highest gene diversity with a value of 0.829 among all the studied loci. The studied population showed genetic relatedness with the populations of Madhya Pradesh, Uttar Pradesh, Jharkhand, and Himachal Pradesh.

The uptake of forensic DNA testing technologies in Africa has been slow despite the revolutionary technology being discovered and adopted 3 decades ago. African governments and partners have invested in construction and equipping of forensic laboratories in Africa but the benefits are yet to be realised as the laboratories are still faced with the challenge of shortage of adequately trained personnel. This paper describes an innovative multidisciplinary training approach that was developed and used to train officers from the Directorate of Criminal Investigations Kenya. We report on the structure, implementation and effectiveness of the training. It is expected that with the increased number of trained forensic DNA analysts, there will be an improvement in quality of forensic DNA evidence presented in courts and a reduction in backlog in the forensic biology laboratories in Kenya.

Mixture analysis of complex forensic DNA mixtures can identify multiple individuals who cannot be excluded using massively parallel sequencing (MPS) with single-nucleotide polymorphism (SNP...

The collection and detection of ‘background’ DNA (bDNA) from items submitted for forensic DNA sampling is a common occurrence when sampling surfaces for DNA left behind following an activity of interest. There are a number of factors that might affect the presence of bDNA on a surface, one of which is cleaning of the surface. Here, we investigate the impact of household cleaning methods on the presence of bDNA on flooring in five homes occupied by known and unrelated individuals. Two adjacent samples were collected pre- and post-cleaning from areas of high and low activity on floors within the kitchen, living room, bedroom and bathroom (i.e. four samples per room). Floors were cleaned by the participant according to their normal routine, with methods and products varying between rooms and homes. Overall, slightly greater quantities of DNA were obtained from samples taken prior to cleaning compared to post-cleaning. Further, major contributors were more frequently assigned in profiles from samples obtained pre-cleaning, although the number of contributors was generally greater in these profiles. This study highlights the need to consider domestic cleaning histories of a surface from which a sample is collected.

The advent of DNA profiling in the 1980s has revolutionised forensic science. Forensic DNA profiling is a powerful tool that is used to both exonerate and implicate persons of interest in criminal ...

Background: Miao people are an officially recognised ethnic group living in southwest China, but have seldom been studied genetically, especially with respect to mtDNA data.Aim: To investigate the sequences and haplogroups of the mtDNA control region in a typical Miao population, with the aim of providing a good start for the expansion of the East Asian mtDNA reference database for forensic DNA analysis.Subjects and methods: We analysed 203 Miao individuals, looking at mtDNA control region sequences. We calculated and illustrated the haplotype frequencies, haplogroup distribution and pairwise Fst values between the Miao and six other worldwide populations to explore genetic polymorphisms and population relationships.Results: We observed 121 haplotypes with corresponding frequencies ranging from 0.0049 to 0.0690 in the Miao population. All the samples were assigned to 71 different haplogroups. The haplotype diversity and the random match probability were estimated to be 0.9844 and 0.0204, respectively. The pairwise Fst values and associated p values among seven populations suggest that the Miao population has significant differences to the other six populations, and is relatively isolated compared with them.Conclusions: Our results suggest that frequency estimates for mtDNA haplotypes in Miao ethnic groups should be determined independently rather than being pooled with other populations.

The Microreader™ 20A ID system is designed for forensic applications such as personal identification, parentage testing, and research. It includes 13 combined DNA index system (CODIS) short tandem repeat (STR) loci (CSF1PO, FGA, TH01, TPOX, vWA, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, and D21S11), three expanded CODIS STR loci (D12S391, D19S433, and D2S1338), three non-CODIS STR loci (D6S1043, Penta D, and Penta E), and the amelogenin locus in one reaction with a six-dye fluorescent (FAM, HEX, TAMAR, ROX, PUR, and QD550) analysis system. In this study, the Microreader™ 20A ID system was validated according to the Scientific Working Group on DNA Analysis Methods validation guidelines for forensic DNA Analysis methods and Chinese national standard, including PCR-based studies, sensitivity study, precision, and accuracy evaluation, stutter calculation, inhibitor tests, species specificity, and DNA mixture studies. Our results suggest that the Microreader™ 20A ID system is a useful tool for personal identification and parentage testing.

Ramos and Gonzalez-Rodriguez introduce the concept of calibration in order to determine whether a system of evidence presentation is a reliable assessor of evidential weight. In this paper, we appl...

In jurisdictions throughout the United States, law enforcement personnel have not been routinely submitting sexual assault kits (SAKs) for forensic DNA testing. The biological evidence in t...

The Huaxia™ Platinum Kit for short tandem repeat (STR) amplification was designed to meet the needs of the rapidly growing Chinese forensic database. This PCR multiplex allows simultaneous amplification of the following autosomal loci: D3S1358, vWA, D16S539, CSF1PO, TPOX, D8S1179, D21S11, D18S51, Penta E, D2S441, D19S433, TH01, FGA, D22S1045, D5S818, D13S317, D7S820, D6S1043, D10S1248, D1S1656, D12S391, D2S1338, Penta D and the gender-identification markers Yindel, and AMEL. The Huaxia™ Platinum Kit enables direct amplification from blood and buccal samples stored on treated and untreated paper, and features an optimized PCR protocol that yields time to results in less than 45 min. Developmental validation testing followed SWGDAM guidelines and demonstrated that this assay produces reproducible and accurate results. Studies on 798 individuals in 4 major Chinese ethnic groups produced highly concordant results with other commercially available STR genotyping kits. The validation results demonstrate that the Huaxia™ Platinum Kit is a robust and reliable identification system for forensic DNA databasing applications.

Cartridges, bullets, and casings (CBCs) are commonly recovered after shooting incidents and could provide valuable DNA information from touch DNA that has been left behind during handling of bullets and loading of guns. Direct PCR, in which the DNA extraction and quantification steps are bypassed, has been shown to provide comparable and sometimes better results from touch DNA and trace DNA samples. Here, direct PCR was applied to touch DNA retrieved from bullet casings from three ammunition types and guns. The results were evaluated to determine whether the technique should be recommended as a standard operating protocol for forensic DNA analysts. Three experiments were carried out to investigate the following: the effect of firing bullets on DNA deposited on bullet casings; the effect of gun and ammunition types on short tandem repeat (STR) profile quality; and the feasibility of using direct PCR in real-world cases via typing of mock casework samples. DNA extraction resulted in a loss of about 40% of DNA originally deposited, and firing a bullet reduced the amount of DNA recovered by 27%. Using the direct PCR protocol, conventional extraction protocol, and dilution protocol on touch DNA from fired bullet casings, we recovered means (and 95% credible intervals), respectively, of 11.1 (7.9–13.9), 5.6 (3.0–7.7), and 2.3 (0.2–4.0) alleles. No statistical difference in alleles recovered was observed between different calibers of ammunition fired from three guns (9 mm, 7.62 mm, and 5.56 mm from Glock Model 19, AK47, and Tavor T-21, respectively). As expected, mixed DNA profiles were observed in 40% of the mock casework samples, in which guns were shared between volunteers. This study showed that direct amplification of touch DNA from bullet casings improved STR profiles. As direct PCR is quicker, cheaper, and resulted in more alleles recovered, forensic DNA analysts may benefit from using direct PCR.

Crown Copyright © 2019 Published by Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 12 month embargo from date of publication (March 2019) in accordance with the publisher’s archiving policy, Standard practice in forensic science is to compare a person of interest’s (POI) reference DNA profile with an evidence DNA profile and calculate a likelihood ratio that considers propositions including and excluding the POI as a DNA donor. A method has recently been published that provides the ability to compare two evidence profiles (of any number of contributors and of any level of resolution) comparing propositions that consider the profiles either have a common contributor, or do not have any common contributors. Using this method, forensic analysts can provide intelligence to law enforcement by linking crime scenes when no suspects may be available. The method could also be used as a quality assurance measure to identify potential sample to sample contamination. In this work we analyse a number of constructed mixtures, ranging from two to five contributors, and with known numbers of common contributors, in order to investigate the performance of using likelihood ratios for mixture to mixture comparisons. Our findings demonstrate the ability to identify common donors in DNA mixtures with the power of discrimination depending largely on the least informative mixture of the pair being considered. The ability to match mixtures to mixtures may provide intelligence information to investigators by identifying possible links between cases which otherwise may not have been considered connected.

O uso de marcadores moleculares para a identificação humana é uma estratégia aplicada nas atividades forenses no Brasil. A criação de bancos de perfis genéticos é uma tendência mundial. É esperado que o uso de tais dados não somente facilite a investigação de casos criminais, mas também leve à redução da criminalidade. O presente artigo objetiva-se realizar uma análise transdisciplinar sobre o Banco Nacional de Perfis Genéticos (BNPG), abordando a funcionalidade dele, apresentando também as técnicas moleculares aplicadas, além de suscitar discussões jurídicas geradas com a implantação do banco de dados nacional. Trata-se de uma revisão bibliográfica exploratória que foi elaborada a partir de uma pesquisa realizada em bases de dados bibliográficos como SciELO, PubMed e JusBrasil. A conscientização da funcionalidade potencial dessa ferramenta poderá despertar o interesse de mais especialistas de ambas as áreas, biológica e jurídica, para que possam aperfeiçoá-la e, futuramente, desenvolver outras aplicações.Palavras-Chave: Identificação Humana; DNA Forense; Banco de Dados; Ciências Forenses; Lei 12.654/12. AbstractThe use of molecular markers for human identification is a strategy applied in forensic investigation in Brazil. The creation of DNA databases is a worldwide trend. It is expected that the use of such data will not only assist investigation of criminal cases, but also lead to reduced crime. The present article aims to carry out a transdisciplinary analysis about the Brazilian National Genetic Profile Database, addressing its functionality, presenting also applied molecular techniques, as well as raising legal discussions generated with the implementation of the national DNA database. It is an exploratory bibliographic review that was elaborated from a research carried out in bibliographic databases like SciELO, PubMed and JusBrasil. Awareness of the potential functionality of this tool may raise the interest of more specialists in both biological and legal areas so that they can improve it and promote it in the future.Keywords: Human Identification; Forensic DNA; Database; Forensic Science; Law 12.654/12.

The Kingdom of Bahrain is one of the few countries that has significant numbers of terrorist investigations, which has allowed our scientists to develop expertise in the forensic examination of post and pre-blast explosive exhibits. This paper presents a review of forensic investigations into improvised explosive device (IED) cases in the Kingdom of Bahrain from 2011. A total of four IED investigations were reviewed (i.e Directionally focused charges (DFC), Directional Focused Fragmentation Charge (DFFC) and Explosively formed penetrator/ projectiles (EFP). DNA recovery utilized different collection methods, such as swabbing, tape lifting, wiping and direct cutting of certain separated parts of the IEDs. Samples were extracted and purified with magnetic beads chemistry and quantified. Low copy DNA extracts were subjected to different concentration steps, and DNA extracts were amplified and processed for detection to obtain reliable results. Using the results of the study, we have developed the concept of Forensic DNA Intelligence, which involves the extraction of human cells deposited in low copy number in challenging areas within the evidence which can lead to significant results. This article will be very useful and informative to assist the forensic community in terrorism cases applications worldwide. Continued efforts must be made to re-evaluate standard operating protocols with empirical studies.

As an important aspect of epigenetics, DNA methylation has been proven to be suitable for forensic DNA analysis. By detecting changes in DNA methylation, it is desirable to construct a model of age patterns associated with it to infer the age of the individual. The hTERT gene methylation is closely related to tumors, but there are few reports on the relationship between hTERT gene promoter methylation and age. In this study, we utilized the methylation-specific polymerase chain reaction and real-time PCR (relative quantification and absolute quantification) approach to explore the connection between hTERT DNA methylation and age prediction. We fit three models for age prediction based on methylation assay for 90 blood samples from donors aged 1–79 years old. Among them, the model of absolute quantification of real-time enabled the age prediction with R2 = 0.9634. We verified the linear regression model with a validation set of 30 blood samples where prediction average error was 4.29 years. Generally, this reliable method improves the DNA methylation analysis of forensic samples.

Modern interpretation strategies typically require an assignment of the number of contributors (N) to a DNA profile. This can prove to be a difficult task, particularly when dealing with higher order mixtures or mixtures where one or more contributors have donated low amounts of DNA. Differences in the assigned N at interpretation can lead to differences in the likelihood ration (LR). If the number of contributors cannot reasonably be assigned, then an interpretation of the profile may not be able to be progressed. In this study, we investigate mixed DNA profiles of varying complexity and interpret them altering the assigned N. We assign LRs for true- and non- contributors and compare the results given different assignments of N over a range of mixture proportions. When a component of a mixture had a proportion of at least 10%, a ratio of at least 1.5:1 to the next highest component, and a DNA amount (as determined by STRmix™) of at least 50 rfu, the LR of the component for a true contributor was not significantly affected by varying N and was therefore suitable for interpretation and the assignment of an LR. LRs produced for minor contributors were found to vary significantly as the assigned N was changed. These heuristics may be used to identify profiles suitable for interpretation.

Review article presents essential information on DNA databases, forensic genomics for human identification and suspect characteristics. Author reports the essential information on the topic of forensic DNA databases and data processing. DNA databases are important tools for the improvement of performance of the security organizations and services with a final goal of national security enhancement.

Ancestry informative SNPs (AISNPs) are genetic variants that exhibit substantially different frequencies between populations from different geographical regions; thus, they can provide some valuable information regarding samples and be used in predicting an individual's ancestry origin. In this study, we selected the potentially best SNPs from our previous study with genome-wide high-density SNP data in mainland Chinese Uygur and Han populations and investigated the allele distribution patterns and genetic information of AISNPs with a mass spectrometry-based SNP genotyping panel. Mass spectrometry-based detection technology offers the opportunity to analyze forensic DNA samples and obtain SNP variants with accuracy and ease. The panel can distinguish and cluster Han and Uygur populations and is suitable for human identification and parentage testing in the two populations. Heatmap, PCA, and Structure analyses indicated that the ideal 64 AISNPs can collectively provide additional information on differences among populations from East Asia, South Asia, Europe and Africa. Additionally, the results proved that the Uygur population is the admixture of East Asia and Europe.

Law enforcement is moving from targeted forensic DNA analysis to more extensive use of genomics in support of criminal investigations and for related purposes, such as the identification of human r...

Purpose Sexual offenders often commit more than one sexual assault, but there is variability in how many assaults they commit and in what pattern over time. Trajectory modeling studies typically use criminal history records as a data source to model perpetrators' sexual assault convictions, but this may underestimate the scope of offending because so few sexual assaults result in a conviction. Method We used both criminal history records and forensic DNA evidence from sexual assault kits (SAKs; also termed ‘rape kit’) to identity a sample of n = 392 serial offenders, all of whom were suspected of committing two or more sexual assaults. Results Using growth mixture models, we identified and validated a four-class model of suspected serial sexual offending spanning ages 16 to 60. The four classes varied in the overall number of sexual assaults committed by each perpetrator and the ages of peak offending. All classes included sexual assaults identified through rape kit testing and through criminal history records. Conclusions Forensic DNA testing of rape kits can help identify suspected serial sexual offenders. DNA testing plus criminal history searches on identified offenders as standard investigation practice would provide police with a more complete picture of offenders' criminal behavior.

Since the emergence of forensic DNA profiling and the corollary creation of DNA databases, efforts to maximise the efficiency and utility of DNA technology have intensified. Such efforts are expedient given the imperative that expenditure on DNA should be cost-effective and the benefits demonstrable. The practice of retaining DNA profiles in databases, either obtained from individuals involved in criminal investigations, or retrieved from suspected crime scenes, has spread globally. The UK's National DNA Database (NDNAD), created in 1995, is both one of the longest established, and biggest of such forensic DNA databases internationally. As such, it is instructive to look at whether there is evidence to demonstrate the effectiveness of this DNA database. This paper thus examines efforts to gauge the effectiveness of forensic DNA databases, concluding that while the UK NDNAD may have led directly to convictions in high profile crimes, its broader impact upon public security goals remains elusive. Keywords: Effectiveness, National DNA database, Criminal investigation, Public security

Evaluative reporting provides a balanced approach to evidence interpretation. The use of evaluative reporting in forensic DNA analysis is common practice and well understood in Australia and New Ze...

Forensic evidence is often quantified by statisticians in terms of a likelihood ratio. When the evidence consists of a DNA match, the likelihood ratio is equal to the reciprocal of the ‘random match probability’ (p). When p is small (e.g. 1/10 million), the likelihood ratio is large (e.g. 10 million to 1). However, when a single match is obtained by searching a database, the prior odds that the forensic DNA was deposited by the matcher can be extremely low, in which case the posterior odds can be low as well despite the high likelihood ratio. Unfortunately, prosecutors, judges and jurors are at risk of misinterpreting the likelihood ratio as the posterior odds, a pervasive reasoning error known as base-rate neglect. Here, we propose a solution to that problem, which consists of evaluating the prior odds based on a case-independent estimate of the size of the active criminal population derived from database search statistics. The posterior odds that the forensic DNA belongs to the unidentified single-matcher can then be calculated (avoiding base-rate neglect).

Firearm-related exhibits are often found at crime scenes. These exhibits may include the firearm, cartridges, cartridges cases or bullets. As ammunition needs to be handled to load the weapon, rega...