The Application of Statistical Modelling to the Interpretation of Complex DNA Profiles
The Application of Statistical Modelling to the Interpretation of Complex DNA Profiles

Author: Hannah Mary Kelly

Publisher:

Published: 2013

Total Pages: 400

ISBN-13:

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In forensic DNA analysis a profile is typically produced from a biological sample collected from the scene of a crime and compared with the DNA of one or more persons of interest (POI). Single source pristine profiles are relatively easy to interpret and their analysis has achieved worldwide acceptance as a reliable scientific method. However, profiles from crime scenes are frequently compromised in quality, or quantity or both. Stochastic factors are often present in compromised profiles which complicate interpretation. Stochastic factors can include; heterozygous balance, allelic dropout, and increased stutter peaks and are characteristic of low template DNA (LtDNA) samples. Complicating interpretation even further is that in many cases, crime scene samples are composed from two or more people. The number of contributors can be unclear. The presence of three or more alleles at any locus signals the existence of more than one contributor, although it can be difficult to distinguish between the presence of a low level second contributor and stochastic effects. This research investigates the behaviour of LtDNA profiles. The traditional guidelines, used in conventional DNA interpretation, are investigated with respect to their application to LtDNA profiles. Statistical models are created for; heterozygous balance, dropout, and stutter. These models use the explanatory variables identified in the data exploratory section of this research to describe the behaviour of each of the aforementioned stochastic effects. These models have been built with the aim that they will be implemented in a probabilistic approach to DNA interpretation. This research also examines different approaches for the interpretation of forensic DNA profiles and the available methods for the calculation of the weight of the evidence of the profile. A two person LtDNA mixture is interpreted using different methods and the resulting statistics are presented. This is done with the aim of demonstrating how the same LtDNA evidence can be interpreted differently under current interpretation guidelines. It is important that that limits of current interpretation models are understood and are not extended beyond their means.

Forensic Practitioner's Guide to the Interpretation of Complex DNA Profiles
Forensic Practitioner's Guide to the Interpretation of Complex DNA Profiles

Author: Peter Gill

Publisher: Academic Press

Published: 2020-06-10

Total Pages: 532

ISBN-13: 0128205687

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Over the past twenty years, there’s been a gradual shift in the way forensic scientists approach the evaluation of DNA profiling evidence that is taken to court. Many laboratories are now adopting ‘probabilistic genotyping’ to interpret complex DNA mixtures. However, current practice is very diverse, where a whole range of technologies are used to interpret DNA profiles and the software approaches advocated are commonly used throughout the world. Forensic Practitioner’s Guide to the Interpretation of Complex DNA Profiles places the main concepts of DNA profiling into context and fills a niche that is unoccupied in current literature. The book begins with an introduction to basic forensic genetics, covering a brief historical description of the development and harmonization of STR markers and national DNA databases. The laws of statistics are described, along with the likelihood ratio based on Hardy-Weinberg equilibrium and alternative models considering sub-structuring and relatedness. The historical development of low template mixture analysis, theory and practice, is also described, so the reader has a full understanding of rationale and progression. Evaluation of evidence and statement writing is described in detail, along with common pitfalls and their avoidance. The authors have been at the forefront of the revolution, having made substantial contributions to theory and practice over the past two decades. All methods described are open-source and freely available, supported by sets of test-data and links to web-sites with further information. This book is written primarily for the biologist with little or no statistical training. However, sufficient information will also be provided for the experienced statistician. Consequently, the book appeals to a diverse audience Covers short tandem repeat (STR) analysis, including database searching and massive parallel sequencing (both STRs and SNPs) Encourages dissemination and understanding of probabilistic genotyping by including practical examples of varying complexity Written by authors intimately involved with software development, training at international workshops and reporting cases worldwide using the methods described in this book

Statistical DNA Forensics
Statistical DNA Forensics

Author: Wing Kam Fung

Publisher: John Wiley & Sons

Published: 2008-04-15

Total Pages: 262

ISBN-13: 9780470727034

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Statistical methodology plays a key role in ensuring that DNA evidence is collected, interpreted, analyzed and presented correctly. With the recent advances in computer technology, this methodology is more complex than ever before. There are a growing number of books in the area but none are devoted to the computational analysis of evidence. This book presents the methodology of statistical DNA forensics with an emphasis on the use of computational techniques to analyze and interpret forensic evidence.

Weight-of-Evidence for Forensic DNA Profiles
Weight-of-Evidence for Forensic DNA Profiles

Author: David J. Balding

Publisher: John Wiley & Sons

Published: 2015-07-20

Total Pages: 233

ISBN-13: 111881455X

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DNA evidence is widely used in the modern justice system. Statistical methodology plays a key role in ensuring that this evidence is collected, interpreted, analysed and presented correctly. This book is a guide to assessing DNA evidence and presenting that evidence in a courtroom setting. It offers practical guidance to forensic scientists with little dependence on mathematical ability, and provides the scientist with the understanding they require to apply the methods in their work. Since the publication of the first edition of this book in 2005 there have been many incremental changes, and one dramatic change which is the emergence of low template DNA (LTDNA) profiles. This second edition is edited and expanded to cover the basics of LTDNA technology. The author's own open-source R code likeLTD is described and used for worked examples in the book. Commercial and free software are also covered.

Weight-of-Evidence for Forensic DNA Profiles
Weight-of-Evidence for Forensic DNA Profiles

Author: David J. Balding

Publisher: John Wiley & Sons

Published: 2005-04-08

Total Pages: 198

ISBN-13: 0470867663

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Assessing Weight-of-Evidence for DNA Profiles is an excellent introductory text to the use of statistical analysis for assessing DNA evidence. It offers practical guidance to forensic scientists with little dependence on mathematical ability as the book includes background information on statistics – including likelihood ratios – population genetics, and courtroom issues. The author, who is highly experienced in this field, has illustrated the book throughout with his own experiences as well as providing a theoretical underpinning to the subject. It is an ideal choice for forensic scientists and lawyers, as well as statisticians and population geneticists with an interest in forensic science and DNA.

Interpreting Complex Forensic DNA Evidence
Interpreting Complex Forensic DNA Evidence

Author: Jane Moira Taupin

Publisher: CRC Press

Published: 2019-11-14

Total Pages: 162

ISBN-13: 1351023772

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Interpreting Complex Forensic DNA Evidence is a handy guide to recent advances—and emerging issues—in interpreting complex DNA evidence and profiles for use in criminal investigations. In certain cases, DNA cannot be connected to a specific biological material such as blood, semen or saliva. How or when the DNA was deposited may be an issue. The possibility of generating DNA profiles from touched objects, where there may not be a visible deposit, has expanded the scope and number of exhibits submitted for DNA analysis. With such advances, and increasing improvements in technological capabilities in testing samples, this means it is possible to detect ever smaller amounts of DNA. There are also many efforts underway to seek was to interpret DNA profiles that are sub-optimal—either relative to the amount required by the testing kit and, potentially, the quality of the obtained sample. Laboratories often use enhancements in order to obtain a readable DNA profile. The broad-reaching implications of improving DNA sensitivity have led to this next, emerging generation of more complex profiles. Examples partial profiles that do not faithfully reflect the proposed donor, or mixtures of partial DNA from multiple people. A complexity threshold has been proposed to limit interpretation of poor-quality data. Research is now addressing the interpretation of transfer of trace amounts of DNA. Complex issues are arising in trial that need to be reconciled as such complexity has added challenges to the interpretation of evidence and its introduction or dismissal in certain cases in the courts. Key Features: Addresses DNA transfer, from person-to-person as well as to objects Outlines each stage required to produce a DNA profile from an exhibit—including collection, handling, storage, and analysis Discusses ethics, subjectivity, and bias—including cognitive dissonance—as they relate specifically to complex DNA evidence Highlights current techniques and the latest advances in DNA analysis, including advances in familial DNA searches Interpreting Complex Forensic DNA Evidence provides tools to assist the criminal investigator, forensic expert, and legal professional when posed with a DNA result in a forensic report or testimony. The result—and any associated statistic—may not reveal any ambiguity, complexity, or the assumptions involved in deriving it. Questions from resolved criminal cases are posed, and the relevant forensic literature, provided for the reader to assess a DNA result and any associated statistic. Case studies throughout illustrate concepts and emphasize the need for conclusions in the forensic report that are supported by the data.

Forensic DNA Evidence Interpretation
Forensic DNA Evidence Interpretation

Author: John S. Buckleton

Publisher: CRC Press

Published: 2018-09-03

Total Pages: 452

ISBN-13: 1315360128

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Now in its second edition, Forensic DNA Evidence Interpretation is the most comprehensive resource for DNA casework available today. Written by leaders in the fields of biology and statistics, including a contribution from Peter Gill, the father of DNA analysis, the book emphasizes the interpretation of test results and provides the necessary formulae in an easily accessible manner. This latest edition is fully updated and includes current and emerging techniques in this fast-moving field. The book begins by reviewing all pertinent biology, and then provides information on every aspect of DNA analysis. This includes modern interpretation methods and contemporary population genetic models available for estimating DNA frequencies or likelihood ratios. Following a chapter on procedures for validating databases, the text presents overviews and performance assessments of both modern sampling uncertainty methods and current paternity testing techniques, including new guidelines on paternity testing in alignment with the International Society for Forensic Genetics. Later chapters discuss the latest methods for mixture analysis, LCN (ultra trace) analysis and non-autosomal (mito, X, and Y) DNA analysis. The text concludes with an overview of procedures for disaster victim identification and information on DNA intelligence databases. Highlights of the second edition include: New information about PCR processes, heterozygote balance and back and forward stuttering New information on the interpretation of low template DNA, drop models and continuous models Additional coverage of lineage marker subpopulation effects, mixtures and combinations with autosomal markers This authoritative book provides a link among the biological, forensic, and interpretative domains of the DNA profiling field. It continues to serve as an invaluable resource that allows forensic scientists, technicians, molecular biologists and attorneys to use forensic DNA evidence to its greatest potential.

The Evaluation of Forensic DNA Evidence
The Evaluation of Forensic DNA Evidence

Author: National Research Council

Publisher: National Academies Press

Published: 1996-12-12

Total Pages: 270

ISBN-13: 0309134404

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In 1992 the National Research Council issued DNA Technology in Forensic Science, a book that documented the state of the art in this emerging field. Recently, this volume was brought to worldwide attention in the murder trial of celebrity O. J. Simpson. The Evaluation of Forensic DNA Evidence reports on developments in population genetics and statistics since the original volume was published. The committee comments on statements in the original book that proved controversial or that have been misapplied in the courts. This volume offers recommendations for handling DNA samples, performing calculations, and other aspects of using DNA as a forensic toolâ€"modifying some recommendations presented in the 1992 volume. The update addresses two major areas: Determination of DNA profiles. The committee considers how laboratory errors (particularly false matches) can arise, how errors might be reduced, and how to take into account the fact that the error rate can never be reduced to zero. Interpretation of a finding that the DNA profile of a suspect or victim matches the evidence DNA. The committee addresses controversies in population genetics, exploring the problems that arise from the mixture of groups and subgroups in the American population and how this substructure can be accounted for in calculating frequencies. This volume examines statistical issues in interpreting frequencies as probabilities, including adjustments when a suspect is found through a database search. The committee includes a detailed discussion of what its recommendations would mean in the courtroom, with numerous case citations. By resolving several remaining issues in the evaluation of this increasingly important area of forensic evidence, this technical update will be important to forensic scientists and population geneticistsâ€"and helpful to attorneys, judges, and others who need to understand DNA and the law. Anyone working in laboratories and in the courts or anyone studying this issue should own this book.

Informing Biological Models for Probabilistic Methods of DNA Profile Interpretation
Informing Biological Models for Probabilistic Methods of DNA Profile Interpretation

Author: Jo-Anne Bright

Publisher:

Published: 2015

Total Pages: 271

ISBN-13:

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The interpretation of forensic DNA profiles is complicated when they are poor quality or have low quantities of DNA, and the presence of DNA from more than one individual. There is a significant diversity in the methods used by laboratories to interpret profiles. These methods use different amounts of the data available within the profile. This diversity has been shown to lead to varying or contradictory conclusions being drawn from the same evidence. Probabilistic methods are being advocated as the way forward as they use more of the information within the profile and they help improve with the consistency of results between analysts. Barriers to the uptake of probabilistic software within forensic laboratories include a lack of understanding of the methods and uncertainties in the limits of the software and software implementation requirements. This thesis uses statistical methods to develop biologically informed models to assist with DNA interpretation of both autosomal and lineage markers. Models have been developed within this thesis using empirical data to predict the expected height of allelic and stutter peaks. These models are intended for use within probabilistic software. A number of topics relating to the implementation of such software are examined. In addition, the effect of linked loci on match probabilities is explored. This work has previously been published as 16 separate papers which have been reproduced within this thesis as one cohesive body of work. A majority of the models have also now been implemented in the commercial software product "STRmix" which is currently being sold worldwide.

Forensic DNA Profiling
Forensic DNA Profiling

Author: Jo-Anne Bright

Publisher: CRC Press

Published: 2019-12-09

Total Pages: 242

ISBN-13: 0429672918

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DNA testing and its forensic analysis are recognized as the “gold standard” in forensic identification science methods. However, there is a great need for a hands-on step-by-step guide to teach the forensic DNA community how to interpret DNA mixtures, how to assign a likelihood ratio, and how to use the subsequent likelihood ratio when reporting interpretation conclusions. Forensic DNA Profiling: A Practical Guide to Assigning Likelihood Ratios will provide a roadmap for labs all over the world and the next generation of analysts who need this foundational understanding. The techniques used in forensic DNA analysis are based upon the accepted principles of molecular biology. The interpretation of a good-quality DNA profile generated from a crime scene stain from a single-source donor provides an unambiguous result when using the most modern forensic DNA methods. Unfortunately, many crime scene profiles are not single source. They are described as mixed since they contain DNA from two or more individuals. Interpretation of DNA mixtures represents one of the greatest challenges to the forensic DNA analyst. As such, the book introduces terms used to describe DNA profiles and profile interpretation. Chapters explain DNA extraction methods, the polymerase chain reaction (PCR), capillary electrophoresis (CE), likelihood ratios (LRs) and their interpretation, and population genetic models—including Mendelian inheritance and Hardy-Weinberg equilibrium. It is important that analysts understand how LRs are generated in a probabilistic framework, ideally with an appreciation of both semicontinuous and fully continuous probabilistic approaches. KEY FEATURES: • The first book to focus entirely on DNA mixtures and the complexities involved with interpreting the results • Takes a hands-on approach offering theory with worked examples and exercises to be easily understood and implementable by laboratory personnel • New methods, heretofore unpublished previously, provide a means to innovate deconvoluting a mixed DNA profile, assign an LR, and appropriately report the weight of evidence • Includes a chapter on assigning LRs for close relatives (i.e., “It’s not me, it was my brother”), and discusses strategies for the validation of probabilistic genotyping software Forensic DNA Profiling fills the void for labs unfamiliar with LRs, and moving to probabilistic solutions, and for labs already familiar with LRs, but wishing to understand how they are calculated in more detail. The book will be a welcome read for lab professionals and technicians, students, and legal professionals seeking to understand and apply the techniques covered.