Biological Basis for DNA Evidence, Peter Gill and John Buckleton Historical and Background Biology Understanding PCR Profiles A Framework for Interpreting Evidence, John Buckleton The Frequentist Approach The Logical Approach The Full Bayesian Approach A Possible Solution A Comparison of the Different Approaches Population Genetic Models, John Buckleton Product Rule Simulation Testing Discussion of the Product Rule and the Subpopulation Model A Complex Case Example - DNA Evidence and Orethral James Simpson Relatedness, John Buckleton and Christopher Triggs Conditional Probabilities Joint Probabilities The Unifying Formula The Effect of Linkage Validating Databases, John Buckleton Which Is the Relevant Population? Population Databases Validating the Population Genetic Model Estimating Q Descriptive Statistics for Databases Sampling Effects, John Buckleton and James Curran Bounds and a Level Methods for Assessing Sampling Uncertainty Minimum Allele Probabilities Discussion of the Appropriateness of Sampling Uncertainty Estimates Mixtures, Tim Clayton and John Buckleton Frequentist Approaches Bayesian Approaches Statistical Evaluation of Mixtures Low Copy Number, John Buckleton and Peter Gill Changes in LCN Profile Morphology The Interpretation of LCN Profiles Non-autosomal Forensic Markers, Simon Walsh, SallyAnn Harbison, and John Buckleton Forensic Mitochondrial DNA Typing Forensic Y Chromosome Analysis Forensic X Chromosome Analysis A Famous Case Example - The Romanovs Parentage Testing, John Buckleton, Tim Clayton, and Chris Triggs Evaluation Of Evidence Paternity Trios: Mother, Child and Alleged Father Non-autosomal DNA Use of the Sub-Population Model of Balding and Nichols to Evaluate the Paternity Index Relatedness in Paternity Cases Multiple Children Inconsistencies in the Mendelian Pattern 'Exclusions' Paternity Trios: Mother, Child and Alleged Father Considering the Possibility of Silent (Null) Alleles Disaster Victim Identification, Identification of Missing Persons, and Immigration Cases, John Buckleton, Chris Triggs, and Tim Clayton Mitochondrial or Nuclear DNA? Human Remains - Obtaining a Profile from Bodily Remains Extraction of DNA from Bone, Tooth, Hair and Nail Complicating Factors DNA Intelligence Databases, Simon Walsh and John Buckleton A Brief History Functional Aspects Legislation Aspects of Forensic Significance Social and ethical considerations Interpretation Issues Associated with DNA Databases

Forensic DNA Evidence Interpretation

DNA analysis is frequently used to acquire information from biological material to aid enquiries associated with criminal offences, disaster victim identification and missing persons investigations. As the relevance and value of DNA profiling to forensic investigations has increased, so too has the desire to generate this information from smaller amounts of DNA. Trace DNA samples may be defined as any sample which falls below recommended thresholds at any stage of the analysis, from sample detection through to profile interpretation, and can not be defined by a precise picogram amount. Here we review aspects associated with the collection, DNA extraction, amplification, profiling and interpretation of trace DNA samples. Contamination and transfer issues are also briefly discussed within the context of trace DNA analysis. Whilst several methodological changes have facilitated profiling from trace samples in recent years it is also clear that many opportunities exist for further improvements.

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Forensic trace DNA: a review

Contents. Preface. 1 Introduction to forensic genetics. Forensic genetics. A brief history of forensic genetics. References. 2 DNA structure and the genome. DNA structure. Organization of DNA into chromosomes. The structure of the human genome. Genetic diversity of modern humans. The genome and forensic genetics. Tandem repeats. Single nucleotide polymorphisms. Further reading. References. 3 Biological material - collection, characterization and storage. Sources of biological evidence. Collection and handling of material at the crime scene. Identification and characterization of biological evidence. Evidence collection. Sexual and physical assault. Presumptive testing. Storage of biological material. References. 4 DNA extraction and quantification. DNA extraction. DNA extraction from challenging samples. Quantification of DNA. DNA IQTM system. References. 5-The polymerase chain reaction. The evolution of PCR-based profiling in forensic genetics. DNA replication - the basis of the PCR. The components of PCR. The PCR process. PCR inhibition. Sensitivity and contamination. The PCR laboratory. Further reading. References. 6 The analysis of short tandem repeats. Structure of STR loci. The development of STR multiplexes. Detection of STR polymorphisms. Interpretation of STR profiles. Further reading. References. 7-Assessment of STR profiles. Stutter peaks. Split peaks (+/- A). Pull-up. Template DNA. Overloaded profiles. Low copy number DNA. Peak balance. Mixtures. Degraded DNA. References. 8 Statistical interpretation of STR profiles. Population genetics. Deviation from the Hardy-Weinberg equilibrium. Statistical tests to determine deviation from the Hardy-Weinberg equilibrium. Estimating the frequencies of STR profiles. Corrections to allele frequency databases. Which population frequency database should be used? Conclusions. Further reading. References. 9 The evaluation and presentation of DNA evidence. Hierarchies of propositions. Likelihood ratios. Two fallacies. Comparison of three approaches. Further reading. References. 10 Databases of DNA profiles. The UK national DNA Database. International situation. Useful web sites. References. 11 Kinship testing. Paternity testing. Identification of human remains. Further reading. References. 12 Single nucleotide polymorphisms. SNPs - occurrence and structure. Detection of SNPs. SNP detection for forensic applications. Forensic applications of SNPs. SNPs compared to STR loci. Further reading. References. 13 Lineage markers. Mitochondria. Applications of mtDNA profiling. The Y chromosome. Forensic applications of Y chromosome polymorphisms. Further reading. Useful web sites. Appendix 1 Forensic parameters. Appendix 2 Useful web links. Glossary. Abbreviations. Index.

An Introduction to Forensic Genetics

Recovery of trace DNA and its application to DNA profiling of shoe insoles.

The successful recovery of trace or contact DNA is highly variable. It is seemingly dependent on a wide range of factors, from the characteristics of the donor, substrate and environment, to the delay between contact and recovery. There is limited research on the extent of the effect these factors have on trace DNA analysis. This study investigated the persistence of trace DNA on surfaces relevant to the investigation of burglary and robbery offences. The study aimed to limit the number of variables involved to solely determine the effect of time on DNA recovery. Given that it is difficult to control the quantity of DNA deposited during a hand contact, human buffy coat and DNA control solution were chosen as an alternative to give a more accurate measure of quantity. Set volumes of these solutions were deposited onto outdoor surfaces (window frames and vinyl material to mimic burglary and ‘bag snatch' offences) and sterile glass slides stored in a closed environment in the laboratory, for use as a control. Trace DNA casework data was also scrutinised to assess the effect of time on DNA recovery from real samples. The amount of DNA recovered from buffy coat on the outdoor surfaces declined by approximately half over two weeks, to a negligible amount after six weeks. Profiles could not be obtained after two weeks. The samples stored in the laboratory were more robust, and full profiles were obtained after six weeks, the longest time period tested in these experiments. It is possible that profiles may be obtained from older samples when kept in similarly favourable conditions. The experimental results demonstrate that the ability to recover DNA from human cells on outdoor surfaces decreases significantly over two weeks. Conversely, no clear trends were identified in the casework data, indicating that many other factors are involved affecting the recovery of trace DNA. Nevertheless, to ensure that valuable trace evidence is not lost, it is recommended that crime scenes are processed expeditiously.

J.F. Hamilton

Papers

The New Zealand DNA databank: its development and significance as a crime solving tool.