Interpreting Complex Forensic DNA Evidence

179 Pages·2019·3.904 MB·\179

by  Jane Moira Taupin (Author)

Interpreting Complex
Forensic DNA Evidence
Interpreting Complex
Forensic DNA Evidence

Interpreting Complex
Forensic DNA Evidence
Jane Moira Taupin
CRC Press
Taylor & Francis Group
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Contents
Preface ix
Acknowledgments xiii
Author xv
1 Complex DNA Evidence 1
1.0 Introduction 1
1.1 Simple versus Complex DNA Evidence 2
1.2 Increased Sensitivity 4
1.3 Increased Technology 6
1.4 Uncertainty 7
1.4.1 Illusion of Scientific Certainty 7
1.4.2 DNA Profile “Match” 8
1.5 History of Exhibit or Provenance and Context 9
1.6 Trace DNA 10
1.7 The “Silo” Effect 12
1.8 Conclusion 12
References 13
2 Complex DNA Profiles 15
2.0 Introduction 15
2.1 The Derivation of a DNA Profile 18
2.2 How Long Does It Take to Obtain a DNA Profile? 20
2.3 DNA Profile Comparison 21
2.3.1 Simple Single-Source DNA Profiles 21
2.3.2 The Sex Marker Amelogenin 22
2.3.3 Autosomal Markers 25
2.3.4 Artifacts 25
2.3.5 Stutter 25
2.3.6 Degraded DNA Profiles 26
2.3.7 Inhibited DNA profiles 26
2.4 DNA Mixture Profiles 27
2.4.1 Number of Contributors 27
2.4.2 Complex DNA mixtures 28
v
vi Contents
2.5 Low-Level DNA and Partial DNA Profiles 29
2.5.1 Stochastic Effects 31
2.5.2 Repeat Analysis 33
2.6 Dropout 34
2.7 Dropin 36
2.8 Complexity Threshold 36
2.9 Enhanced Interrogation 37
2.10 Direct PCR 37
2.11 Rapid DNA 37
References 38
3 Statistical Evaluation of Complex DNA Evidence 41
3.0 Introduction 41
3.1 Statistical Interpretation and Wording 43
3.2 Errors During Analysis 45
3.3 Errors of Interpretation or in Conveying the Statistical
Meaning 47
3.3.1 Transposition of the Conditional 47
3.3.2 Association Error 49
3.4 Statistics: Weight-of-Evidence for DNA Profiles 52
3.4.1 Likelihood Ratio 53
3.4.2 Formulation 53
3.4.3 Framework of Circumstances 55
3.4.4 Binary to Continuous Models 55
3.5 Probabilistic Genotyping 56
3.5.1 Variability between Systems 57
3.5.2 Variability within the Same System 57
3.5.3 Application to the Real World 58
3.5.4 Specificity 61
3.5.5 Validation 61
3.5.6 Open Source versus Closed Source Computer
Software Programs 62
3.6 Hierarchy of Propositions 62
3.7 Fallacious Reasoning 64
3.7.1 Assumption of Independence 64
3.7.2 Combining Multiple Pieces of Diverse Evidence 66
References 67
4 Transfer 71
4.0 Introduction 71
4.1 Transfer Principles 74
4.2 Trace DNA 79
Contents vii
4.3 Trace DNA Transfer 79
4.4 Tertiary and Higher Levels of Transfer 82
4.5 Persistence, Prevalence, and Recovery 83
4.5.1 Persistence, Prevalence, and Recovery in Context 84
4.5.2 Persistence 84
4.5.3 Prevalence and “Background DNA” 85
4.5.4 Non-Self DNA 87
4.5.5 Detection and Recovery 88
4.6 Skin 89
4.6.1 Skin DNA 89
4.6.2 Shedder Status 90
4.7 Hands and Fingernails 91
4.7.1 Hands 91
4.7.2 Fingernails 92
4.8 “Wearer” DNA 94
4.9 Investigator-Mediated Transfer 95
4.10 Extrapolating Experimental Data to Casework 95
4.11 Direct versus Indirect Transfer Estimations 96
References 97
5 Integrity 101
5.0 Introduction 101
5.1 Documentation 103
5.2 The Scene Environment 104
5.3 Personal Protection Equipment 106
5.4 The Mortuary 109
5.5 Packaging, Handling, and Transport 109
5.6 Crime Scene Laboratories 110
5.7 Fingerprint Laboratories 111
5.8 Forensic Laboratory Examination 112
5.9 Staff Reference Samples 119
5.9.1 Laboratory Staff Contamination 120
5.9.2 Police-Staff Contamination 122
5.10 History 125
5.10.1 Laundering of Clothing and
Other Fabric Items 126
5.11 Controls 128
References 129
6 Familial DNA Searching 133
6.0 Introduction 133
6.1 Searching DNA Databases 135
viii Contents
6.2 Familial DNA Searching 135
6.2.1 Introduction of Familial DNA Searching 135
6.2.2 Techniques Used 139
6.3 SNP Testing 143
6.4 Ancestry DNA Databases 144
6.5 Long-Range or Extended Familial DNA Searching
(Also Known As Genetic Genealogy) 145
6.6 Forensic DNA Phenotyping and Epigenetics 148
6.7 Rogue DNA Databases 149
References 150
Glossary of Terminology 153
Index 159
Preface
Aims: This book provides a guide to recognizing and interpreting the com-
plex DNA evidence that is now used in criminal investigations.
Increasing improvements in technology have enabled ever smaller
amounts of DNA to be analyzed and interpreted. For example, it is com-
mon practice for forensic laboratories to obtain a DNA profile from a dozen
human cells or fewer. These DNA profiles may be sub-optimal for the quan-
tity required by the testing kit and/or the quality obtained.
Sometimes DNA evidence may be obtained from a deposit that may
not be tested for, or cannot be related to, a specific biological material such
as blood, semen, or saliva. The possibility of generating DNA profiles from
touched objects, where there may not be a visible deposit, has expanded the
scope of exhibits submitted for DNA analysis in a forensic laboratory.
When deposits of biological material are not visible, either with the
naked eye or through microscopic techniques, physical characteristics that
may be informative, such as shape and size of the deposit, are lacking. In
addition, speculation such as swabbing surfaces with no visible deposits may
be employed in sampling.
Sacrificing the confirmatory (or indeed presumptive) testing step for spe-
cific biological material may be a consequence of the analysis of very small
amounts of sample. If there is a non-visible deposit and it is speculated that
DNA may be present, the whole sample is submitted for DNA profiling with
the ultimate aim of obtaining a result. No further testing may be performed
or, indeed, available due to lack of sample. Resulting consequences are an
increased uncertainty and complexity in understanding and conveying the
meaning of the DNA evidence.
A consequence of improving DNA sensitivity to detect ever smaller
amounts of DNA is the generation of more complex DNA profiles to inter-
pret. There may be partial profiles that do not faithfully reflect the proposed
donor DNA profile, or mixtures of partial DNA from many people.
Caution has been advised in the literature for criminal investigations
in both determining the source of unknown DNA at a crime scene and the
interpretation of mixed DNA profiles. Contamination issues have been high-
lighted regarding the collection and analysis before receipt at the forensic
laboratory, and from cold case investigations where the continuity is unclear
ix