An expert is one who knows more and more about less and less until they know absolutely everything about nothing...

(First part by Nicholas Butler, Bartlett's 585:10)

The work is its own reward.

(Sherlock Holmes, The Adventure of the Norwood Builder)

Several significant things have happened since the first edition of Forensic DNA Typing was published in January 2001. The Human Genome Project published a draft sequence of the human genome in February 2001 and completed the 'finished' reference sequence in April 2003. In addition, human mitochondrial DNA population genomics is underway and more than a thousand full mitochondrial genomes have been published. Technology for DNA sequencing and typing continues to advance as does our understanding of genetic variation in various population groups around the world. These milestones are a tribute to the progress of science and will benefit the field of forensic DNA typing.

The literature on the short tandem repeat (STR) markers used in forensic DNA testing has more than doubled in the four years since writing the first edition. More than 2000 publications now detail the technology and report the allele frequencies for forensically-informative STR loci. Hundreds of different population groups have been studied; new technologies for rapidly typing DNA samples have been developed, and standard protocols have been validated in laboratories worldwide. Yet DNA results are still sometimes challenged in court - not usually because of the technology, which is sound - but rather the ability of practitioners to perform the tests carefully and correctly. A major purpose of this book is to help in the training of professionals in the field of forensic DNA testing. The knowledge of forensic scientists, lawyers, and students coming into the field will be enhanced by careful review of the materials found herein.

The advent of modern DNA technology has resulted in the increased ability to perform human identity testing. Individual identification is desirable in a number of situations including the determination of perpetrators of violent crime such as murder and rape, resolving unestablished paternity, and identifying remains of missing persons or victims of mass disasters.

In the past few years, the general public has become more familiar with the power of DNA typing as the media has covered efforts in identifying remains from victims of the World Trade Center twin towers collapse following the terrorist attacks of 11 September 2001, the O.J. Simpson murder trial, the President Clinton-Monica Lewinsky scandal, and the identification of the remains in the Tomb of the Unknown Soldier. In addition, our perceptions of history have been changed with DNA evidence that revealed Thomas Jefferson may have fathered a child by one of his slaves.

These cases have certainly attracted widespread media attention in recent years, however, they are only a small fraction of the thousands of forensic DNA and paternity cases that are conducted each year by public and private laboratories around the world. The technology for performing DNA typing has evolved rapidly since the 1990s to the point where it is now possible to obtain results in a few hours on samples with only the smallest amount of biological material.

This book will examine the science of current forensic DNA typing methods by focusing on the biology, technology, and genetic interpretation of short tandem repeat (STR) markers, which encompass the most common forensic DNA analysis methods used today. The materials in this book are intended primarily for two audiences: forensic scientists who want to gain a better understanding of STRs and professionals in the law enforcement and legal communities who find it hard to comprehend the complexities of DNA profiling. This text should also directly benefit college students learning more about forensic DNA analysis in an academic environment. The references cited at the end of each chapter provide a fairly comprehensive view of this dynamic field.

This book is also intended to aid forensic DNA laboratories in meeting the training requirements stated in the DNA Advisory Board Quality Assurance Standards. These standards are striving to improve the quality of work performed in forensic laboratories by requiring technical managers and DNA examiners to have training in biochemistry, genetics and molecular biology in order to gain a basic understanding of the foundation of forensic DNA analysis. See Standard 5.2.1 and 5.3.1 in Appendix IV of this book.


Since the first edition was written in the winter months of 2000, the published literature has grown dramatically on the topic of STR typing and its use in forensic DNA testing. With more than 2000 papers now available describing STR markers, technology for typing these STRs, and allele frequencies in various populations around the world, the scientific basis for forensic DNA typing is sound. The basic foundational material in the first edition is still relevant and thus has remained essentially unchanged. However, ten new chapters have been added to accommodate the explosion of new information since the turn of the century.

New topics such as single nucleotide polymorphisms (SNPs) and Y chromosome testing have gained greater acceptance within the forensic community since 2000 and therefore have become areas of expansion in this edition. A very comprehensive look at mitochondrial DNA and its application to forensic DNA analysis is included in Chapter 10. There is updated information on new DNA extraction procedures, real-time PCR for DNA quantification, multi-capillary electrophoresis instruments, and 5-dye chemistries that are now used in many forensic DNA laboratories. Citations have expanded to include more than 500 new literature references enabling readers to find original source material or to conduct extensive background research on the various topics covered herein and more than 50 new figures and 45 new tables containing helpful information have been added in this second edition of Forensic DNA Typing.

Statistical issues with data analysis and interpretation that were missing in the first edition are covered in Chapters 19-23 in this new edition. Extensive examples are provided for each equation discussed and corresponding population data can be found in Appendix II to enable readers to review the source of conclusions reached. Another appendix includes the description of a hypothetical case from start to finish in an attempt to bring together the information discussed throughout the book and to aid in training students and professionals in the field.

In this edition, we utilize Data, Notes, and Applications (D.N.A.) Boxes to cover specific topics of general interest. Many of the high-profile cases included in the last chapter of the first edition, such as the O.J. Simpson trial, are now scattered throughout the book near the sections dealing with the science or issues behind these cases. It is hoped that these D.N.A. Boxes will help readers see the practical value of forensic DNA typing.


The book has been divided into three primary sections covering the biology, technology, and statistical analysis (genetics) of STR markers. Within each section, the chapters progress from basic introductory information to on-going 'cutting-edge' research. The first few chapters in particular are meant as introductory material for those readers who might be less familiar with DNA or as a review of useful materials for more advanced readers. The biology section is contained in Chapters 2 through 11, the technology section involves Chapters 12 through 18, and the genetics section may be found in Chapters 19 to 23. The final chapter examines the use of DNA testing in mass disaster victim identification efforts, which include the greatest national tragedy in U.S. history, the events of 11 September 2001.

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