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 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.

Biological Sequence Analysis
Biological Sequence Analysis

Author: Richard Durbin

Publisher: Cambridge University Press

Published: 1998-04-23

Total Pages: 372

ISBN-13: 113945739X

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Probabilistic models are becoming increasingly important in analysing the huge amount of data being produced by large-scale DNA-sequencing efforts such as the Human Genome Project. For example, hidden Markov models are used for analysing biological sequences, linguistic-grammar-based probabilistic models for identifying RNA secondary structure, and probabilistic evolutionary models for inferring phylogenies of sequences from different organisms. This book gives a unified, up-to-date and self-contained account, with a Bayesian slant, of such methods, and more generally to probabilistic methods of sequence analysis. Written by an interdisciplinary team of authors, it aims to be accessible to molecular biologists, computer scientists, and mathematicians with no formal knowledge of the other fields, and at the same time present the state-of-the-art in this new and highly important field.

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

Author: David J. Balding

Publisher: John Wiley & Sons

Published: 2015-05-18

Total Pages: 233

ISBN-13: 1118814541

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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.

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.

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.

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.

DNA Technology in Forensic Science
DNA Technology in Forensic Science

Author: National Research Council

Publisher: National Academies Press

Published: 1992-02-01

Total Pages: 199

ISBN-13: 0309045878

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Matching DNA samples from crime scenes and suspects is rapidly becoming a key source of evidence for use in our justice system. DNA Technology in Forensic Science offers recommendations for resolving crucial questions that are emerging as DNA typing becomes more widespread. The volume addresses key issues: Quality and reliability in DNA typing, including the introduction of new technologies, problems of standardization, and approaches to certification. DNA typing in the courtroom, including issues of population genetics, levels of understanding among judges and juries, and admissibility. Societal issues, such as privacy of DNA data, storage of samples and data, and the rights of defendants to quality testing technology. Combining this original volume with the new update-The Evaluation of Forensic DNA Evidence-provides the complete, up-to-date picture of this highly important and visible topic. This volume offers important guidance to anyone working with this emerging law enforcement tool: policymakers, specialists in criminal law, forensic scientists, geneticists, researchers, faculty, and students.

Forensic DNA Trace Evidence Interpretation
Forensic DNA Trace Evidence Interpretation

Author: Duncan Taylor

Publisher: CRC Press

Published: 2023-05-30

Total Pages: 583

ISBN-13: 1000801381

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Forensic DNA Trace Evidence Interpretation: Activity Level Propositions and Likelihood Ratios provides all foundational information required for a reader to understand the practice of evaluating forensic biology evidence given activity level propositions and to implement the practice into active casework within a forensic institution. The book begins by explaining basic concepts and foundational theory, pulling together research and studies that have accumulated in forensic journal literature over the last 20 years. The book explains the laws of probability - showing how they can be used to derive, from first principles, the likelihood ratio - used throughout the book to express the strength of evidence for any evaluation. Concepts such as the hierarchy of propositions, the difference between experts working in an investigative or evaluative mode and the practice of case assessment and interpretation are explained to provide the reader with a broad grounding in the topics that are important to understanding evaluation of evidence. Activity level evaluations are discussed in relation to biological material transferred from one object to another, the ability for biological material to persist on an item for a period of time or through an event, the ability to recover the biological material from the object when sampled for forensic testing and the expectations of the prevalence of biological material on objects in our environment. These concepts of transfer, persistence, prevalence and recovery are discussed in detail in addition to the factors that affect each of them. The authors go on to explain the evaluation process: how to structure case information and formulate propositions. This includes how a likelihood ratio formula can be derived to evaluate the forensic findings, introducing Bayesian networks and explaining what they represent and how they can be used in evaluations and showing how evaluation can be tested for robustness. Using these tools, the authors also demonstrate the ways that the methods used in activity level evaluations are applied to questions about body fluids. There are also chapters dedicated to reporting of results and implementation of activity level evaluation in a working forensic laboratory. Throughout the book, four cases are used as examples to demonstrate how to relate the theory to practice and detail how laboratories can integrate and implement activity level evaluation into their active casework.