UNIVERSAL LAW AND GENETICS
-UNIVERSAL LAW AND GENETICS
THE FUTURE DEVELOPMENT OF DNA EVIDENCE IN THE
AUSTRALIAN CRIMINAL JUSTICE SYSTEM
MARCUS SMITH
A thesis submitted for the degree of Doctor of Philosophy of The Australian National University
UNIVERSAL LAW AND GENETICS
-ORIGINALITY STATEMENT
This Thesis is my own work; except where otherwise acknowledged. This Thesis, in
whole or in part, has not been submitted for any other degree at any other university.
- UNIV ERSAL LAW AND GENETICS
ACKNOWLEDGEMENTS
Writing this Thesis has been a stimulating and rewarding endeavour. I am grateful to a
number of people who have provided assistance at key stages and enabled its
completion. Whilst work of this nature is at times a solitary pursuit, it could not have
been completed in isolation and the contribution of others has played a vital role.
I would like to acknowledge the support of my principal supervisor Dr Gregor Urbas of
the Australian National University College of Law, and thank him for his assistance. He
has been an exceptional supervisor over the past two years. I am grateful for his
guidance in selecting my topic and structuring the Thesis, meeting with me to discuss
the arguments of the Thesis and suggesting relevant materials, exercising academic
judgement and providing advice on the drafts of the chapters and the Thesis as a whole,
and most recently, assisting me to make the transition into the next stage of my life. His
ability to do this in addition to many other academic and personal commitments is
demonstrative of his high capacity and I would highly recommend him as a supervisor.
I would like to thank my advisors, Associate Professor Molly O’Brien of the Australian
National University College of Law, and Associate Professor Jeremy Gans of the
University of Melbourne Law School. Their advice has significantly improved the
Thesis and brought to light important additional perspectives. I would also like to
acknowledge the assistance that Emeritus Professor Jim Davis of the Australian
National University College of Law has provided at key stages throughout this period. It
has been a privilege to complete my Thesis in this environment and to have been guided
by individuals of this calibre.
UNIVERSAL LAW AND GENETICS
-There are many others who have supported and inspired the production of this Thesis. I
would like to acknowledge their contribution and note that they have facilitated my
personal development over this period. This endeavour has provided a great opportunity
for intellectual and personal growth and is one that I would wholeheartedly recommend.
-Universallawandgeneiics
-Es bildet ein Talent sich in der Stille, Sich ein Charakter in dem Strom der Welt.
Goethe (1790)
UNIVERSAL LAW AND GENETICS
-ABSTRACT
DNA evidence is the most significant advancement in the history of forensic science,
and has rapidly become a vital part of the modem criminal justice system. Despite its
strong scientific foundation, there remain aspects of its use that have been controversial.
This Thesis investigates the future development of DNA evidence in the Australian
criminal justice system, and discusses strategies for improvement. Following an
examination of the scientific and historical background to an investigation of this
nature, the Thesis considers theoretical and practical arguments for and against the
implementation of a universal forensic DNA database in Australia, which would include
the DNA profiles of the entire resident population. It then discusses the current legal
issues associated with DNA evidence in Australia and major overseas jurisdictions such
as the United Kingdom and the United States. The legal issues discussed include those
related to the inclusion of DNA profiles in DNA databases; the collection, testing and
storage of DNA evidence; the presentation of DNA evidence at trial; and the use of
DNA evidence in the review of criminal convictions and acquittals. The Thesis
discusses how the future implementation of a universal forensic DNA database could
resolve current legal issues arising in these four areas. It makes a number of novel
findings that could be applied in most modem criminal justice systems. The Thesis
concludes by proposing an integrated approach to the regulation of this developing area
of law.
UNIVERSAL LAW AND GENETICS
-CONTENTS
INTRODUCTION
16CHAPTER ONE - SCIENTIFIC FOUNDATION
INTRODUCTION 25
I HISTORICAL DEVELOPMENT OF DNA PROFILING 27
A Scientific Advancement 27
B Legal Recognition 30
II SCIENTIFIC BACKGROUND ON BIOLOGICAL MATERIAL 34
A Cellular Biology 34
B Molecular Biology 37
C Genetics 40
III SCIENTIFIC BASIS OF DNA PROFILING 42
A Sample Collection and Extraction 42
B Polymerase Chain Reaction 45
C Short Tandem Repeat Analysis 47
D DNA Separation and Detection 50
E Low Copy Number DNA Testing 52
F Y-Chromosome Analysis 53
G Mitochondrial DNA Analysis 53
H Single Nucleotide Polymorphisms 54
I Areas o f Future Development 56
UNIVERSAL LAW AND GENETICS
-IV MATHEMATICAL BASIS OF DNA PROFILING 57
A Probability 57
B Statistics 60
C Population Genetic Modelling 61
CONCLUSION 67
CHAPTER TWO - THEORETICAL
PERSPECTIVES
INTRODUCTION 73
I MORAL AND POLITICAL PHILOSOPHY 75
A Contractualisrn 75
B Consequentialism 79
C Deontology 82
D Justice, Liberty and Community 85
II PHILOSOPHY OF SCIENCE 92
A Deduction, Induction and Empiricism 93
B Falsification 95
C Scientific Revolution 97
III REGULATION OF SCIENCE 99
X Scientific Discourse 100
B Conflating Science and Law 102
C Genetic Information 105
CONCLUSION 109
-- Univi RSAL law and Genetics
CHAPTER THREE - FORENSIC DNA DATABASES:
DETERMINING THE EXTENT OF INCLUSION
INTRODUCTION 114
I FUNDAMENTAL ISSUES CONCERNING DNA DATABASES 116
A Defining DNA Databases 116
B Ownership o f DNA Profiles 117
II EXISTING FORENSIC DNA DATABASES 120
A Australia 120
B United Kingdom 123
1 Success Rate 124
2 Public Debate 125
C United States 129
1 Californian Legislation 129
2 Constitutionality 130
3 Expanding the Data Set 131
III PROPOSAL FOR A UNIVERSAL FORENSIC DNA DATABASE 133
A Supporting A rguments 13 3
1 Proposal 133
2 Enhanced Policing and Community Safety 136
3 Equitability 137
4 Continued Expansion o f Existing Databases 138
UNIVERSAL LAW AND GENETICS
-B Counter Arguments 140
1 Genetic Screening 140
2Discrimination 143
3Informed Consent 145
4Governmental Considerations 146
5Presumption o f Innocence 148
6 False Positives 149
IV BEYOND IDENTITY: PHENOTYPIC TRAITS AND FAMILIAL MATCHING 152
A Non Coding DNA and Phenotype 152
B Physical Traits 153
C Genes and Behaviour 157
D Genes and Crime 159
E Familial Matching 164
CONCLUSION 168
CHAPTER FOUR - LEGAL ISSUES IN THE COLLECTION,
TESTING AND RETENTION OF FORENSIC BIOLOGICAL
MATERIAL
INTRODUCTION 173
I OWNERSHIP RIGHTS IN FORENSIC BIOLOGICAL MATERIAL 174
II SURVEY OF LAW GOVERNING THE COLLECTION OF FORENSIC
BIOLOGICAL MATERIAL 179
-A Australia 180
1 Harmonisation o f State Laws 180
2 Commonwealth Forensic Procedures Laws 180
B United Kingdom 186
C United States 194
D New Zealand 196
E Europe 197
1 Germany 197
2 Denmark 198
3 Ireland 199
III C O L L E C T IO N OF FO R E N SIC B IO L O G IC A L M A T E R IA L 200
A Requesting Samples from Volunteers 200
B Collection o f Crime Scene Samples 204
C Collection o f Samples in Other Contexts 207
IV T E S T IN G AND R E T E N T IO N OF FO R E N SIC B IO L O G IC A L M A T E R IA L 210
A Testing Forensic Biological Material 210
1 Australian Cases o f Laboratory Error 211
2 Labelling Errors 214
3 Coincidental Matching 215
B Retention and Management o f Forensic Biological Material 216
C Privacy Considerations Associated with Forensic Biological Material 219
C O N C L U SIO N 223
- Universallawand Genetics
UNIVERSAL LAW AND GENETICS
-CHAPTER FIVE - LEGAL ISSUES IN THE PRESENTATION OF
DNA EVIDENCE AT TRIAL
IN T R O D U C T IO N 229
I P R IN C IPL E S OF E V ID E N C E 231
A F o u n d a tio n s o f E v id e n c e L a w 231
B R e le v a n c e 232
C U n fa irly P r e ju d ic ia l E v id e n c e 233
D E x p e r t E v id e n c e 235
E S ta n d a r d s f o r S c ie n tific E v id e n c e 238
1 U n ite d S ta te s 2 3 9
2 A u s tr a lia 243
II D N A E V ID E N C E AT T R IA L 245
A F e a tu r e s o f D N A E v id e n c e 245
B S ta tis tic s a n d F a lla c ie s 24 6
C C iv il P r o c e e d in g s 251
III K E Y D N A E V ID E N C E C A SE S 2 5 4
A O v e r s e a s C a se L a w 25 4
1 U n ite d S ta te s 25 4
2 U n ite d K in g d o m 255
UNIVERSAL LAW AND GENETICS
-B Australian Cases 257
1 Key Cases: Tran 257
2 Key Cases: Lucas 258
3 Key Cases: Jarrett 259
4 Key Cases: Pantoja 261
5 Key Cases: Milat 262
6 Key Cases: Karger 263
7 Key Cases: Sing 265
8 Key Cases: Lisoff 266
9 Key Cases: Button 267
IV PROPOSALS FOR IMPROVING TRIAL OUTCOMES 269
A Assisting the Jury 269
B Limiting the Misrepresentation o f Scientific Evidence 272
1 Witnesses 272
2 Prosecutors and Defence Lawyers 275
C Education Programs 277
CONCLUSION 279
CHAPTER SIX - DNA EVIDENCE AND THE REVIEW OF
CONVICTIONS AND ACQUITTALS IN THE CRIMINAL
j u s t i c e
S
y s t e mINTRODUCTION 284
I CORRECTING WRONGFUL CONVICTIONS 286
-A Judicial Review 288
1 Unreasonable or Unsafe Verdicts 289
2 Miscarriages o f Justice 290
B Preservation o f Crime Scene Samples 291
C Innocence Projects 294
1 United States 294
2 Australia 296
3 Case Study 298
4 Statistics 300
D DNA Review Panels 301
1 New South Wales 301
2 United Kingdom 304
3 United States 305
E Compensating the Wrongfully Convicted 308
F Developing a National Review Panel for Australia 311
II THE PRINCIPLE OF DOUBLE JEOPARDY 313
A Rationale for the Principle 313
B Legal Basis o f the Principle 315
C Key Case: Carroll 317
III CORRECTING WRONGFUL ACQUITTALS 319
A United Kingdom Legislation 320
B New South Wales Legislation 320
C Queensland Legislation 324
D Model Criminal Code Officers Committee Report 325
E Re-Examining Carroll 327
F The Effect o f a Universal Forensic DNA Database 328
CONCLUSION 331
UNIVERSAL LAW AND GENETICS
UNIX I RSAL LAW AND GENHTICS
-CONCLUSION
335APPENDIX
342BIBLIOGRAPHY
348I JOURNAL ARTICLES, BOOKS AND REPORTS 349
II CASE LAW 366
III LEGISLATION 373
IV HUMAN RIGHTS INSTRUMENTS 376
-- UNIVERSAL Law a n d Gin h tic s
-IN T R O D U C T IO N
-- Universallawandgenetics
-DNA profiling is widely regarded as the most significant scientific advancement in the
history of forensic science, and is a vital aspect of modem criminal investigation.
Despite the strong scientific foundation of DNA profiling, there remain aspects of its
use in the legal system that have been controversial. The Thesis will focus on these
controversial aspects of its current and future use. Internationally, one of the most
widely debated aspects of this area of the law in recent years, has been the expansion of
forensic DNA databases. In the United Kingdom and a number of other developed
countries, governments have continued to expand the categories of individuals who are
included in the databases. In some jurisdictions, this has initiated debate over whether a
universal forensic DNA database, comprised of the DNA profiles of the entire
population, might be a more equitable option, an option that would significantly
increase the investigative capacity of the police. A central aspect of the Thesis will be to
evaluate the advantages and disadvantages of a universal forensic DNA database in the
context of the Australian criminal justice system. This will provide the opportunity to
examine a wide range of current legal issues associated with DNA evidence from a new
perspective.
It should be stated from the outset that the Thesis focuses on DNA evidence in the
criminal justice system, and not on the legal issues associated with the use of genetic
information in healthcare and population health. However, these areas may be
mentioned in the Thesis where relevant. For example, there may be a degree of
interaction between privacy, security, health, and criminal justice issues associated with
the regulation of genetic information. In some cases, existing health databases may be a
resource that can be utilised by the criminal justice system, and where regulatory
structures have already been developed, it is important that a uniform approach to the
regulation of genetic information be considered. The Appendix discusses healthcare and
population health issues in detail and proposes an integrated regulatory approach to
genetic information.
UNIVERSAL LAW AND GENETICS
-The -Thesis can be conceptually divided into three Parts. Part One, consists of Chapter
One and Chapter Two. Chapter One will provide the background scientific and
historical knowledge that is required for the legal analysis throughout the Thesis.
Chapter Two, will discuss the relevant theoretical perspectives, and consider many of
these in the context of a universal forensic DNA database. Part Two, consisting of
Chapter Three will consider the scope of DNA databases, including practical arguments
for and against the establishment of a universal forensic DNA database in Australia, and
a discussion of the type of genetic information that should be included. Part Three of the
Thesis, consisting of Chapters Four, Five and Six, will consider the legal issues raised
by DNA evidence at three key stages in the criminal justice system: the collection and
testing of DNA evidence, the presentation of DNA evidence at trial, and the use of
DNA evidence in the review of convictions and acquittals. Many of the legal issues
considered in Part Three, will be examined in light of the universal forensic DNA
database discussed in Part Two. The Thesis will consider how a universal forensic DNA
database could resolve current legal issues that have arisen in relation to the use of DNA
evidence in the Australian criminal justice system. The Thesis aims to provide an
examination of current, and likely future, legal issues associated with DNA evidence,
and discuss their interrelatedness. Possible solutions to these issues will be proposed in
relation to a universal forensic DNA database, and it is hoped that this will contribute to
the future development of the Australian criminal justice system. The contents of the
Thesis will now be discussed in greater detail.
Chapter One carries out an investigation of the historical development of DNA
profiling, and the scientific basis which has provided the foundation for this
development. An understanding of the scientific background to DNA profiling is
necessary for developing effective legal responses to regulate the use of the technology.
It was not until the mid-twentieth century, when the molecular understanding of
genetics was discovered, that the scientific basis for modem DNA profiling techniques
UNIVERSAL LAW AND GENETICS
-was established. It is only in the last twenty years that techniques which have facilitated
the use of DNA as an identification tool, began to arise. Only in the last fifteen years,
have population databases of DNA profiles been established. The relative novelty of the
science itself, and its legal application, must be kept in mind when considering legal
implications of the technology. Chapter One will also consider relevant scientific
principles, including molecular and cell biology, and genetic inheritance. Finally, it will
discuss the science of DNA profiling, including the processing of samples, techniques
such as polymerase chain reaction, the construction of a DNA profile, and the
mathematical basis of DNA identification.
Chapter Two focuses on the underlying theory and policy that will support the legal
analysis of the substantive Chapters. This theoretical perspective is important in
justifying arguments, and in providing a link to other areas of law and policy. It
provides a foundation for proposed new laws, and is central to the comparison and
evaluation of existing laws. This theory bridges the gap between the disciplines of
science and law throughout the Thesis. The Chapter will begin with some of the
foundational theories of moral and political philosophy, such as contractualism,
consequentialism and deontology. It will also consider the competing political
philosophies of libertarianism and communitarianism. These perspectives will be
applied to the context of a universal forensic DNA database, and theoretical arguments
supporting the proposal will be outlined. Further, it will consider theories from the
philosophy of science which attempt to understand the nature of scientific knowledge
and how it advances, including those of theorists such as Karl Popper and Thomas
Kuhn. Finally, the Chapter will discuss epistemic aspects of science and law, and the
policy approaches which have been applied to genetic information in other legal
contexts.
-- Universal Lawand Genetics
-Chapter Three will investigate the development of forensic DNA databases, and
specifically, the merits of a universal forensic DNA database. It begins by defining a
forensic DNA database and distinguishing it from other types of databases, such as
those used in medical research. The Chapter will consider other fundamental issues,
such as legal ownership of the DNA profiles included in a database. The characteristics
of databases already in operation in Australia and in other jurisdictions such as the
United States and the United Kingdom, will be discussed. Chapter Three will then
investigate the proposition that a universal forensic DNA database should be
implemented in Australia, discussing the arguments for and against. The advantages of
this approach include enhanced policing capability, and reduced unfairness in terms of
the categories of individuals included in the database. Disadvantages include the
potential for the database to be used for future purposes that were not envisaged at the
time the database was constructed. The future prospect of screening the database for
phenotypic and psychological trait information will also be considered.
Chapter Four discusses the legal issues associated with the collection, testing, and
retention of forensic biological material. The legal basis of ownership of this material
will be considered. This will be followed by a comparative discussion of the legislation
governing the collection of this material, primarily in Australia, the United Kingdom
and the United States; but also in a number of European jurisdictions in which data was
available. In the context of Australia, the Commonwealth legislation will be discussed,
as well as the progression of the state-based legislation towards a uniform Australian
approach. The Chapter will then consider the collection of forensic biological material
in Australia. This will include a number of issues, such as whether carrying out the
mass-screening of volunteers contravenes the privilege against self-incrimination, and
how the implementation of a universal forensic DNA database may ameliorate some of
these current issues. Finally, the Chapter will consider a number of key cases in which
-- Unix HRSAL lawandgenetics
issues have arisen during laboratory testing; and management issues such as DNA
testing back-logs, which have recently been problematic in a number of jurisdictions.
Chapter Five will focus on the issues that can arise when DNA evidence is presented at
trial. DNA evidence is often central to the outcome of a case, and must be interpreted in
the context of a range of other evidence, by a fact-finder who usually has no formal
scientific training. The Chapter will include a discussion of the relevant aspects of
Australian law which facilitate the presentation of expert evidence at trial, from the
perspective of the Evidence Act 1995 (Cth); as well as a comparative discussion of the
legal standards for presenting scientific evidence at trial in the United States and the
United Kingdom. This will be followed by a discussion of a number of idiosyncratic
aspects of DNA evidence which have been problematic at trial in the past, including a
discussion of the prosecutor’s fallacy. Again, the potential for a universal forensic DNA
database to resolve some of these problems will be discussed. The Chapter will then
outline key cases that have featured DNA evidence, tracing the legal recognition of the
science itself, as well as techniques and systems that are widely used today, such as the
Profiler Plus system. Many of these cases will consider the effect that a universal
forensic DNA database will have on the issues highlighted. Finally, the Chapter will
consider proposals for improving the way DNA evidence is presented at trial, including
improved education programs, and procedures for presenting DNA evidence.
Chapter Six examines the use of DNA evidence in the review of convictions and
acquittals. Initially, the principle of double jeopardy will be discussed, and the role of
DNA evidence in the recent decisions of a number of governments to limit the
application of the principle. The Chapter will then examine the legal basis for correcting
wrongful acquittals, and reforms that have been enacted in Australia and the United
Kingdom. This will be followed by a discussion of the contribution of DNA evidence in
correcting wrongful convictions, and the role of DNA evidence in a number of high
UNIS I RSAL LAW AND GENETICS
-profile corrections that have occurred. Finally, the role of review panels in investigating
wrongful convictions and acquittals will be discussed, as well as the issue of
compensating the wrongfully convicted, and whether a national review panel would be
suitable for Australia.
In summary, the Thesis intends to conduct a thorough investigation into the use of DNA
evidence in the Australian criminal justice system, including the relevant scientific and
historical background to a study of this nature, and relevant theoretical perspectives.
One aspect of the Thesis will be to compare and contrast the current Australian legal
approach with current and proposed approaches in major overseas jurisdictions. The
United States and the United Kingdom will be given particular attention, due to their
size and the availability of data.
The major focus of the Thesis will be to examine the arguments for and against the
introduction of a universal forensic DNA database, and examine how its introduction
would influence related aspects of the criminal justice system, such as the collection of
DNA evidence, the use of DNA evidence at trial, and the use of DNA evidence in the
review of convictions and acquittals. It will provide an insight into potential future
developments in this area of law and forensic science, and how these may be regulated.
It is hoped that this research, and any publications resulting from it, will add to debate
regarding how this area of the law should progress, and contribute to the future
development of DNA evidence in the Australian criminal justice system.
UNIX I RSAL LAW AND CihNHTICS
-CHAPTER ONE - SCIENTIFIC FOUNDATION
-- Universallawandgenetics
-CHAPTER ONE - SCIENTIFIC FOUNDATION
INTRODUCTION 25
I HISTORICAL DEVELOPMENT OF DNA PROFILING 27
A Scientific Advancement 27
B Legal Recognition 30
II SCIENTIFIC BACKGROUND ON BIOLOGICAL MATERIAL 34
A Cellular Biology 34
B Molecular Biology 37
C Genetics 40
III SCIENTIFIC BASIS OF DNA PROFILING 42
A Sample Collection and Extraction 42
B Polymerase Chain Reaction 45
C Short Tandem Repeat Analysis 47
D DNA Separation and Detection 50
E Low Copy Number DNA Testing 52
F Y-Chromosome Analysis 53
G Mitochondrial DNA Analysis 53
H Single Nucleotide Polymorphisms 54
I Areas o f Future Development 56
IV MATHEMATICAL BASIS OF DNA PROFILING 57
A Probability 57
B Statistics 60
C Population Genetic Modelling 61
CONCLUSION 67
UNIX I RSAL LAW AND GENETICS -INTRODUCTION
Chapter One will investigate the historical development of DNA profiling, and the
science underlying this development. An understanding of the scientific foundation of
DNA profiling is crucial to developing effective legal regulation of the technology in
the context of criminal investigation. Overall, the Chapter will seek to ensure that a
sufficient foundation has been established to ensure that the legal analysis in Chapters
Three, Four, Five and Six of the Thesis can be conducted effectively.
Part One of the Chapter will examine the historical development of genetics, and the
gradual legal recognition of forensic DNA profiling. Whilst modem genetics can be
traced back to the nineteenth-century, when the theory of evolution challenged the
dominant theory of creationism; it was not until the mid-twentieth century, when
genetics at a molecular level began to be understood, that the foundation for forensic
DNA profiling was established. The further development of molecular biology over the
past twenty years, has led to the widespread use of DNA evidence in criminal
identification. This record highlights how rapidly the technology has advanced. Indeed,
it is only in the last ten years that the technology has been sufficiently developed to
enable it to be used in the context of population databases. Legal recognition of the
technology has progressed from its initial use in a United Kingdom mass screening in
the mid-nineteen eighties, through to its high profile application in wrongful conviction
cases in the United States, to the current groundbreaking use of phenotypic analysis to
construct a physical and psychological profile of an unknown suspect.
Part Two of the Chapter will provide the relevant scientific background in relation to
biological material obtained by police from individuals and crime scenes, and subjected
to laboratory analysis. This will include a discussion of the biology of the cell, the basic
structural unit of all living organisms; cell types; and the organisation of cells within the
U N I Vh RS AL LAW AND CiFNF.'I ICS
-human body. This will be followed by a discussion of genetic material within the
nucleus of human cells, and the means by which cells replicate. The discussion will then
consider the basic principles of molecular biology, including the structure of the genetic
code, and how it is converted into protein, the structural component of human cells.
Finally, the principles of genetics that govern the inheritance of traits will be outlined.
Part Three of the Chapter will investigate the science of forensic DNA profiling in
sequential order, beginning with the method of collecting biological material and
extracting the DNA. The procedures that must be adhered to during the collection of
biological material will then be discussed, and the potential for samples to be
contaminated or destroyed will be considered. This will be followed by a discussion of
the polymerase chain reaction (PCR) technique, which has been central to recent
advancements in forensic DNA profiling. The development of the polymerase chain
reaction, which allows the amplification of sections of DNA for analysis, has vastly
improved the ability of scientists to analyse crime scene samples, which are often
degraded due to environmental factors, or only present in trace amounts. The next step
in the process is the identification of short tandem repeats (STRs) of DNA that will be
used for individual identification. Finally, the amplified sequences of DNA must be
separated based on their size, and the resultant pattern observed. The DNA is usually
stained with dye or has florescent markers attached, and is detected by measuring
emitted light. This section will also discuss recent advancements such as Y-
chromosome testing, which is used to determine an individual’s sex; the forensic
application of mitochondrial DNA; and single nucleotide polymorphisms (SNPs,
pronounced ‘snips’).
Part Four of the Chapter will examine the mathematical principles that form the basis of
the match probability used in the presentation of DNA evidence at trial. The basic laws
of probability and statistics that are applied to obtain these results will first be outlined.
UNIVERSAL LAW AND GENETICS
-This will be followed by a discussion of the principles of population genetics that are
used to measure allele frequency, including the Hardy-Weinberg Equilibrium. Finally,
the discussion will consider the evidentiary value of a match between two DNA
profiles.
I HISTORICAL DEVELOPMENT OF DNA PROFILING
A Scientific Development
The origin of modem genetics can be traced back to the nineteenth-century, when
Charles Darwin first published his theory of evolution through natural selection. Darwin
argued that successful organisms differ from unsuccessful organisms, and that those
best suited to their environmental surroundings will survive. He proposed that over
time, this leads to biological differences within species, and the evolution of new
species. 1 2 However, Darwin did not develop a theory of heredity. This followed early in
the twentieth-century when the rediscovered ideas of Gregor Mendel were used to form
the basis of the new science of genetics. By systematically breeding peas, Mendel
observed that physical characteristics are transmitted between generations in a
predictable manner. He found that this was achieved by factors (now called genes) that
remain intact and independent between generations. In the latter half of the twentieth-
century, chemistry was able to provide an explanation for the observations of Darwin
and Mendel.
1 Charles Darwin, On the Origin o f Species (1859).
2 See e.g., Roger Klare, Gregor Mendel: Father o f Genetics (1997).
-- universal Lawandgenetics
In 1944, Oswald Avery discovered that genetic characteristics known as traits, were
transmitted between generations by a molecule called deoxy-ribo-nucleic acid (DNA).1 * 3
Avery’s discovery was followed in 1953 by James Watson and Francis Crick, who
discovered the double-helical structure of DNA 4 In the early 1980s, David Botstein
used a variation in DNA known as restriction fragment length polymorphisms (RFLPs,
pronounced ‘rif-lips’) to propose a method for mapping genes. The method was
subsequently used to identify human disease genes, such as those for Huntington’s
disease, and breast cancer (BRCA1). The restriction fragment length polymorphism
method uses an enzyme to cut the DNA at specific points, enabling the comparison of
samples from different individuals.
In 1984, the English geneticist Alec Jeffreys was using restriction fragment length
polymorphisms to study the genetic basis for human disease, when he made a discovery
that would subsequently revolutionise forensic identification. Jeffreys discovered that
human DNA contained non-coding regions in which specific sequences in the code
were repeated. When these regions were compared in different individuals, it was
observed that whilst they all shared these repeating regions of DNA, the degree of
repetition at each site varied. The repeating units, each consisting of l-to-4 base pairs of
genetic code, are known as microsatellites, and occur throughout the human genome.
Jeffreys also discovered larger and more complex sites known as minisatellites. These
consist of repetitions of between 10 and 100 base pairs, and occur at over 1000 points
throughout the human genome. Collectively, the repetitive regions of DNA were named
variable number tandem repeats (VNTRs).5
1 Avery discovered a ‘transforming principle’ which could cause a heritable change o f bacterial cells: O.T. Avery et al, ‘Studies on the Chemical Nature o f the Substance Inducing Transformation of Pneumococcal Types’ (1944) 79 Journal o f Experimental Medicine 137.
4 J. D. Watson and F. H. C. Crick, ‘Structure for Deoxyribose Nucleic Acid’ (1953) 171 Nature 737. 5 See e.g., A. Jeffreys et al, ‘Individual Specific Fingerprints o f Human D NA’ (1985) 316 Nature 76.
UNIVERSAL L \Y\ AND GENETICS
-In 1986, Kary Mullis developed the polymerase chain reaction method for the
amplification of sections of DNA. Polymerase chain reaction is an enzymatic process
that continually replicates a small section of DNA over a number of cycles. The amount
of DNA increases exponentially with each cycle. Polymerase chain reaction is able to
amplify a sufficient amount of DNA to enable samples from different individuals to be
analysed and compared. Further, it has been an important discovery from the
perspective of forensic science, as it can use minute amounts of biological material
recovered from crime scenes that otherwise could not have been analysed.6
In 1990, the Human Genome Project began, with an expected completion date of 2005.
Its goal was to produce a complete map of the human genome. The work was
undertaken in laboratories throughout the United States, the United Kingdom, and
France. Computer programs were developed to store the vast amount of data in a
meaningful manner. In 2000, it was announced that the first draft had been completed,
and in 2003, the final draft was completed. The project established a number of
important facts, such as the number of genes, 30,000; the similarity between humans,
99.9%; and, that the most common sequence is a single nucleotide polymorphism.7
In the early 1990s, short tandem repeat markers were found to be an effective method
for human identification, due to their high degree of variability between individuals. In
the United Kingdom, a significant research effort was undertaken to study population
variation. A second generation multiplex using the short tandem repeat loci TH01,
VWA, FGA, D8S1179, D18S51, D21S11, and the amelogenin sex indicator, was
established. It formed the basis of the National DNA Database in the United Kingdom
when it was launched in 1995.
6 Kary Mullis, ‘The Unusual Origin of the Polymerase Chain Reaction’ (1990) 262 Scientific American 56-65.
1 See e.g., Kevin Boon, The Human Genome Project: What Does Decoding DNA Mean fo r Us? (2002).
UNIVERSAL LAW AND GENETICS
-The Federal Bureau of Investigation in the United States followed this lead and began
research to establish the short tandem repeat loci that would be used in their Combined
DNA Index System. During this process, 22 laboratories evaluated 17 core loci
provided in a kit from either Promega Corporation or Applied Biosystems. Promega
provided the short tandem repeat markers CSF1PO, TPOX, TH01, VWA, D16S539,
D7S820, D13S317, and D5S818, as the Power Plex 1.1 kit; and Applied Biosystems
provided the markers D3S1358, VWA, FGA, D5S818, D13S317, D7S820, D8S1179,
D21S11, D18S51, and amelogenin, as the Profiler Plus kit. In 1997, 13 of these loci
were selected. Applied Biosystems developed the Identifiler kit on the basis of these
loci. Australia adopted the Profiler Plus kit in 1998. The development of commercial
short tandem repeat kits has been driven by the loci that were initially selected for
inclusion in the national databases of the United Kingdom and the United States. The
cost and availability of these kits is determined by patents.
B Legal Recognition
DNA profiling was first used in 1987, in the Pitchfork case.8 The scientist who
pioneered the technique, Alec Jeffreys, was asked to analyse biological samples
recovered from the bodies of two girls who were raped and murdered in Leicestershire
two years apart, and compare them with a sample provided by Rodney Buckland, who
had confessed to raping and murdering one of the victims. It was found that Buckland’s
DNA did not match the sample recovered from the victim, and he was released. A
screening of a subset of the men from three surrounding villages was conducted.
Following the screening, it emerged that Colin Pitchfork had coerced another man into
providing a sample on his behalf. When Pitchfork’s DNA was compared to that found at
the crime scene, police found that it matched, and he was subsequently convicted.
8 See e.g., Mark Jobling and Peter Gill, ‘Encoded Evidence: DNA in Forensic Analysis’ (2004) 5 Nature Reviews Genetics 739.
-DNA profiling was first accepted at trial in the United States in 1988, in the Florida
District Court of Appeal case of Andrews v State ^ However, it was the New York case
People v Castrop in which DNA profiling was significantly challenged on legal and
scientific grounds. Castro was charged with stabbing a mother and daughter, after blood
recovered from his watch matched the victims’ DNA. The evidence was challenged
under the Frye test, which requires that novel scientific evidence be generally accepted
in the relevant scientific field.* 11 Whilst it was acknowledged in this case that the theory
of DNA profiling was generally accepted by geneticists, it was held that the laboratory
which conducted the testing did not perform the test in compliance with the appropriate
control procedures, and the evidence was not admitted.
The first Australian case to utilise DNA profiling occurred in the Australian Capital
Territory in 1989. Desmond Applebee, a suspect in a sexual assault investigation, was
convicted after his DNA was found to match a sample recovered from a victim.
Following the match, Applebee changed his defence in which he denied any contact
with the victim, stating that they had consensual sex. A random match probability of
one in 165 million was presented by the prosecution, and Applebee was subsequently
convicted. In an Australian case in 1990, Van Hung Tran, biological samples were
sent to Cellmark Diagnostics in the United Kingdom for analysis. However, it was held
that the evidence was inconclusive, and the results were not accepted in Court.
UNIVERSAL LAW AND GENETICS
-9 533 So. 2d 851 (1-988). 10 545 NY Sid 985 (1989).
11 Frye v United States 293 F. 1013 (D.C. Cir. 1923). This case will be discussed in greater detail in Chapter Five.
12 CrimTrac, Key Dates in the history o f DNA Profiling
<http://www.crimtrac.gov.au/systems_projects/KeyDatesintheHistoryofDNAProfiling.html> at 1 February 2010.
13 (1990) 50 A Crim R 233.
-- Universallawandgenetics
-In these early cases, the restriction fragment length polymorphism method was used to
produce the DNA profiles. However, by the mid-1990s, this method had been
superseded by short tandem repeat analysis, in combination with the polymerase chain
reaction. Whilst this method had a significantly larger discriminating power, it was
more susceptible to contamination if the laboratory work was not conducted with
sufficient diligence. The Profiler Plus system was adopted by all Australian
jurisdictions in 1998. The South Australian case R v Karger 4 held that this system was
accepted by the relevant scientific community, and was sufficiently reliable under
Australian law if the procedures are carried out correctly. This finding resulted from a
three month voir dire, in which the technology was examined in detail.
Perhaps the highest profile trial involving DNA evidence in the 1990s was the O.J.
Simpson case in the United States. Simpson was charged with murdering his wife
Nicole Brown, and Ron Goldman in Los Angeles in 1994. There was a great deal of
prima facie evidence indicative of guilt. This included a glove stained with blood found
at his house, and blood stains in his car. DNA profiling indicated that this blood
matched the victims’. At trial, Simpson’s defence team asserted that investigators had
deliberately contaminated the evidence, and placed some of the victims’ blood on the
glove and in his car. They demonstrated that handling of the evidence was improperly
documented, and that it was possible for contamination to have occurred. A verdict of
‘not guilty’ was returned by the jury. A civil proceeding later found that Simpson had
violated the victim’ constitutional rights. This discrepancy can be explained in part by
the differing standard of proof involved in the two cases.15
14 [2002] SASC 294.
15 B.A. Weir, ‘DNA Statistics in the Simpson Matter’ (1995) 11 Nature Genetics 365.
-- Universal Lawandgenetics
-In 2004, the high-profile Australian trial of John Bradley Murdoch in the Northern
Territory Supreme Court also focused on DNA evidence. The Court heard that a small
smear of blood found on a t-shirt belonging to the girlfriend of the victim, Joanne Lees,
was 640 billion times more likely to have come from Murdoch than from an unrelated
individual randomly selected in the Northern Territory. Murdoch was subsequently
convicted.16 This case was also notable for the use of the low copy number (LCN) DNA
testing technique. The technique was challenged in the case by Murdoch, who sought
leave to appeal to the High Court, and has also been challenged in the United
Kingdom.17
The first forensic database of DNA profiles was established in the United Kingdom in
1995, and is known as the National DNA Database (NDNAD). By 2004, this database
contained more than 2.5 million profiles that had been obtained from suspects and
convicted criminals. It currently contains over 5 million profiles. The United Kingdom
Government has reported that hundreds of cases are being solved each month through
‘cold hits’. By the turn of the century, databases had been established in most western
, i o
countries, including Australia, Japan and throughout Europe and North America.
Although the primary application of DNA profiling has been in criminal law, it has been
successfully used in other applications. DNA profiling has begun to be used in
immigration and paternity cases, and for the identification of missing persons. DNA
profiling has also been used to identify soldiers killed at war. For example, the remains
of soldiers from World War II have been exhumed and tested to establish identity more
than fifty years after their death. More recently, the Australian Federal Police used DNA
profiling to identify victims of the 2004 Bali terrorist attacks, and assisted South-East
16 The Queen v Murdoch [2005] NTSC 80 (15 December 2005).
17 See e.g., Eleanor Graham, ‘DNA Reviews: Low Level DNA Profiling’ (2008) 4 Forensic Science, Medicine and Pathology 129.
18 See e.g., United Kingdom Parliamentary Documents
<http://www.parliament.uk/documents/upload/POSTpn258.pdf> at 1 February 2010.
-- universallawandgenetics
-Asian countries to identify victims of the 2004 tsunami.19 DNA testing is now also
widely used in cases of disputed paternity. An industry proffering DNA paternity testing
kits over the internet has recently emerged, along with tests for a range of genetic
disorders.20
An important application of DNA profiling within the legal system has been its use to
establish the innocence of convicted persons. DNA evidence has been used to free over
218 people in the United States, many of whom were on death row awaiting
execution. In Australia, the case of Frank Button, who served time in prison for sexual
assault but was later released on the basis of DNA evidence, has received significant
publicity. DNA evidence has led to a number of jurisdictions legislating to limit the
application of the common law rule against double jeopardy, and establishing innocence
panels to review DNA evidence/3
II SCIENTIFIC BACKGROUND ON BIOLOGICAL MATERIAL
A Cellular Biology
Cells are the fundamental units of living organisms. The relatively simple cells of
bacteria are called prokaryotic cells, while the more complex and highly developed cells
of plants and animals, including humans, are known as eukaryotic cells. The human
body comprises approximately 100 trillion eukaryotic cells. These cells are all produced
19 Above, n 12.
20 See e.g., 23andMe < https://www.23andme.com> at 1 February 2010.
21 See e.g., Innocence Project Website < http://www.innocenceproject.org/> at 1 February 2010. 22 See e.g., Mark Whittaker, ‘A Test o f Innocence’ The Weekend Australian Magazine (Sydney), 18-19 August 2007.
23 See e.g., Crimes Amendment (Double Jeopardy) Act 2006 (NSW). These developments will be discussed in detail in Chapter Six.
-by the division of pre-existing cells. Cells are differentiated into a wide range of forms
and functions. For example, there are distinct bone cells, blood cells, nerve cells, and
skin cells; each with their own characteristics and specialised task. Cells create and
maintain all the anatomical structures, and perform all the physiological functions of the
human body. The cell itself comprises a variety of organelles, such as the nucleus,
responsible for storing genetic information and regulating the cell, and the
mitochondrion, responsible for energy production.
Golgi apparatus Cilia
---Lysosome
--- Mitochondrion
Rough endoplasmic reticulum
Cell membrane
Cytoplasm
Nucleolus
Chromatin
Ribosomes
Smooth endoplasmic reticulum — Nuclear membrane
Centrioles
Microtubules
Figure 1.1 The C ell24
Cytology is the analysis of the internal structures of cells; and histology is the study of
tissues, groups of cells that work together to perform a specific function. The body can
be understood at a number of levels of organisation. Atoms are the smallest stable units
of matter, and combine to form molecules such as water. Molecules combine to form
' 4 Diagrammatic Representation of a Typical Cell in the Human Body
< http://www.teachengineering.org/collection/cub_/lessons/cub_images/cub_cells_lesson01_figure2.jpg> at 1 February 2010.
[image:35.531.4.522.115.795.2]UNIVERSAL LAW AND GENETICS
-organelles, such as the nuclear membrane. Organelles combine to form cells, the
smallest living units in the human body. Cells combine to form tissues, such as muscle
tissue. Tissues combine to form organs, and organs combine to form organ systems.
Relevant organ systems include the cardiovascular and integumentary systems. The
cardiovascular system includes the heart, blood vessels, and blood. Blood serves to
transport oxygen and carbon dioxide, deliver nutrients, remove waste, transport
hormones, assist in temperature regulation, and to provide a defence against disease.
The integumentary system includes the epidermis and dermis, sweat glands, and hair
follicles. Its function is to protect the underlying tissues.
All human cells except mature red blood cells contain a nucleus. There are coiled
threadlike structures known as chromosomes in the cell nucleus. A human being
normally has 23 pairs of chromosomes. One of the 23 pairs determines an individual’s
gender, and these are known as the sex-determining chromosomes. Females have two X
chromosomes, and males have one X and one Y chromosome. The remaining 22 pairs
of chromosomes are called autosomes. Chromosomes are extended strands of DNA
(deoxy-ribo-nucleic acid). The chromosomes are numbered according to size;
chromosome 1 is the largest, and chromosome 22 is the smallest.
There are two kinds of cell division: mitosis and meiosis. Mitosis is the form of cell
division by which cells in the body replicate, grow and differentiate themselves. Mitosis
results in two daughter cells. Each cell produced by mitosis therefore has a chromosome
component of 46, and is known as diploid. Meiosis occurs only in germ-line cells
producing sperm and ova. It results in the formation of reproductive cells called
gametes. Each of these cells has half the normal chromosome complement.
-- Universallawand Genetics
-B Molecular -Biology
DNA (deoxyribo-nucleic acid) has two distinct purposes. First, it replicates itself so that
cells can divide and carry the same genetic information. Second, it carries genes which
provide instructions for the production of proteins required by the organism for their
structure and function. Information carried by DNA is therefore passed on to following
generations of cells within the same human body, and to progeny. DNA consists of a
sequence of four bases which makes up the ‘genetic code’. The pattern of repetition of
these bases determines the order in which amino acids are structured, and thus the type
of protein produced. Proteins build the cellular structure and control the chemical
reactions required by the organism.
DNA is a large, acidic molecule found in the nucleus of the cell, and is primarily
composed of deoxygenated ribose groups. This is the origin of the name ‘deoxy-ribo’,
‘nucleic’, ‘acid’. The DNA molecule consists of two polynucleotide chains that form a
double helix structure. The two chains are hybridised, with individual nucleotides
pairing via hydrogen bonding. Individual nucleotides are comprised of a ribose
molecule, a phosphate molecule, and one of four bases; adenine (A), guanine (G),
cytosine (C) or thymine (T). The bases bond in a complementary manner to form rungs
in the double helix. The base adenine always pairs with its complementary base
thymine, and cytosine always pairs with its complementary base guanine. The hydrogen
bonding holding the two strands together can be disrupted by high temperature or
chemical treatment in a reversible process known as denaturisation.
-U.S. National Library of M ed ic in e
Figure 1.2 DNA 25
At points in the genetic code where genes are located, the code occurs in triplet form.
Each triplet of three bases is known as a codon, and each specifies a particular amino
acid. For example, the triplet of bases TGA codes for the amino acid cysteine. Other
triplets specify to ‘start’ or ‘stop’ reading the gene at a specific point. The number of
triplets varies according to the specific protein, but it is usually between 100 and 1000.
A sequence of base-pairs coding for a particular human structure, function or trait, is
known as a gene. A gene contains the information necessary to express a specific
protein. It is believed that humans have approximately 35,000 genes, each coding for a
different protein. Proteins have diverse roles in the human body. They may have a
structural role, for example, the protein keratin is the main constituent of hair. They can
also have a functional role; for example, the protein salivary amylase is an enzyme that
25 Diagrammatic Representation o f the DNA Molecule
< http://ghr.nlm.nih.gov/handbook/illustrations/dnastructure.jpg> at 1 February 2010.
[image:38.531.7.518.32.813.2]UNIVERSAL LAW AND GENETICS
-aids the digestion of carbohydrates in food. Proteins are composed of chains of amino
acids.
Genes only account for a small proportion of the genome. In humans, over ninety-five
percent of DNA consists of non-coding regions. However, in less complex organisms
such as bacteria, there are no non-coding portions of DNA. It is believed that non
coding DNA may contribute to the complexity of the human genome. One theory is that
it acts as a regulatory system, integrating the activity of genes and proteins. The non
coding regions of the genetic code contain repetitive sequences of DNA. Specific points
in the non-coding regions can be identified by the number of times a particular pattern,
such as TAAGAAT, is repeated. These points serve as markers, and there is sufficient
difference between individuals for them to be used as a basis for identification. Within
genes, there are coding and non-coding portions, named introns and exons. The exons
are protein coding portions of the gene, and these are interspersed with the non-coding
introns.
The entire genetic code of an organism is held within the nucleus of all nucleated cells.
Different genes are activated in each cell depending on the type of cell it is, and the
surrounding conditions. When a specific protein is required by a cell, the DNA for that
gene unwinds and the strands separate. An enzyme called RNA polymerase produces a
complementary copy of one strand of the DNA, called messenger RNA (mRNA). It
transports the coded genetic information out of the nucleus to the ribosomes. These are
the units of the cell that produce proteins. The process of reading the DNA and
producing mRNA is called transcription. At the ribosomes, the amino acids are
assembled in the order specified by the mRNA, forming a protein. This process of
converting the message from mRNA to protein is called translation. The pathway from
DNA, to RNA, to protein, is known as the central dogma o f molecular biology. The
genetic code is universal in the sense that DNA and RNA, and their constituent bases
-- Universallawandgenetics
-Adenine, Thymine, Cytosine, Guanine, and Uracil, are present in the genomes of all
living things, both plant and animal, throughout the natural world.
C Genetics
Different versions of a gene at a specific locus are known as alleles. Alleles occur when
there is a small alteration in the ordering of the bases. This could involve the change of
a single letter, or the deletion, insertion, or repetition of a codon. If the change does not
cause any overall detrimental effect, it is called a polymorphism. Many genetic
variations do not impact on the individual’s physical characteristics or health status, for
example, whether a person’s eyes are brown or blue. However, in the case that the
change results in a faulty gene and causes a problem with the production of a protein, it
is called a mutation. Some mutations result in no protein being produced at all, in other
cases a non-functional or partially functional protein is produced.
-= allele for blue ey e s (recessive)
= allele for brown ey es (dominant)
Individual A: Individual B:
Heterozygous Homozygous
(wil have brown eyes) (for brown eyes)
O ABPI 2007
Individuate: Homozygous (for blue eyes)
Figure 1.3 Alleles 26
All humans have a unique genetic composition known as their genotype. The observable
characteristics of an individual’s genotype may be determined solely by their genetic
composition, or by the interaction of both their genetic composition and the
environment. An example of the latter is height, which is influenced partly by genetic
factors, and partly by nutrition during childhood and adolescence. The observable
characteristics of an individual are known as their phenotype.
Individuals inherit one allele of each gene from each of their parents. An individual is
described as homozygous for a particular gene if the two inherited copies are the same
allele. However, where two different alleles of the gene are inherited, the individual is
described as heterozygous. A recessive trait (often represented by a lower case letter
such as a) is expressed only if an individual is homozygous for both copies of the gene;
one inherited from the mother and one from the father. It is therefore possible for
26
Diagrammatic Representation o f Blue and Brown Alleles fo r Eye Colour
<http://www.abpischools.org.uk/res/coResourceImport/modules/genome/en- images/dominantrecessivealles.gif> at 1 February 2010.
[image:41.531.9.520.25.686.2]UNIVERSAL LAW AND GENETICS
-parents who do not actually express a particular trait, to have a child with that trait if
each parent is a heterozygous carrier for the recessive allele. In the case of recessive
traits, each child has a twenty five percent chance of inheriting both alleles, and
acquiring the trait. A dominant trait (often represented by an upper case letter such as A)
is expressed if an individual is heterozygous. In the case of dominant traits, each child
need only have one dominant allele in a particular gene pair.
An X-linked trait is linked to genes that occur on the X chromosome. Males have an X
and a Y chromosome, and they therefore have a copy of the X chromosome genes, and
will express a mutated copy of one of these genes. A female has two X chromosomes.
Therefore a recessive mutated allele on one X chromosome, may not cause the trait to
be expressed due to a normally functioning allele on the other X chromosome.
Penetrance describes the likelihood that an individual with a specific genetic trait that
could cause a disease, will actually present with it.
Ill SCIENTIFIC BASIS OF DNA PROFILING
A Collection and Extraction o f DNA
As has been discussed, DNA can be recovered from the biological material obtained
from individuals or at crime scenes, and subjected to forensic analysis. The most
common human biological material submitted for testing is blood and semen. Sufficient
DNA can also be recovered from hair, saliva, skin, and sweat; sources such as postage
27 The factual content o f this part o f the Chapter is primarily sourced from John Butler, Forensic DNA Typing (2005), which is the most influential text in this field.
-- Universallawandgenetics
-stamps; and personal items such as a watch, razor or toothbrush. This biological
material can be used to associate or exclude an individual from association with the
crime scene. In order for the results of any subsequent DNA profiling to be used as
evidence in court, the sample collection must accord with procedure, and a chain of
custody must be established.
The transfer of DNA usually involves the suspect’s DNA being deposited on an object
or at a location; or the victim’s DNA being deposited on the suspect’s body or clothing.
The proper collection, transport, and storage of biological material is vital to ensuring
that valid test results are obtained, and that they can be presented in court.
At a crime scene, the forensic scientist must identify whether a sufficient amount of
biological material is present to enable a sample to be taken. For example, a common
test for the presence of human blood is Luminal (3-amino-phthalhydrazide, sodium
carbonate, and sodium perborate). This compound is sprayed on an item in dark
conditions, and luminescence is observed in the presence of blood. There are a number
of measures that can be taken to ensure that the biological material is properly
preserved. Latex gloves, a mask over the nose and mouth, and a hair net should be worn
to avoid contaminating the sample. Samples should be dried to prevent bacterial growth,
packaged separately and numbered with a case and item number, the date, and the
collector’s initials.
To perform comparative DNA profiling, evidence obtained at a crime scene must be
compared with biological material collected from a suspect. The sample is usually
obtained by pressing a cotton tip against the inside of the suspect’s cheek. This
painlessly removes buccal cells. The sample is then taped to collection paper for
28 B. Hopkins et al, ‘The Use o f Mini-satellite Variant Repeat-Polymerase Chain Reaction (MVR-PCR) to Determine the Source o f Saliva on a Used Postage Stamp’ (1994) 39 Journal o f Forensic Sciences 526. 29 M.A. Tahir et al, Proceedings from the Seventh International symposium on Human Identification
(1996), 76.
UNIVERSAL LAW AND GENETICS
-preservation. To reduce deterioration and bacterial growth, the biological material must
be preserved in a cold, dry environment.30
For DNA profiling to be undertaken, the DNA in the sample must be extracted from
cellular protein and other material that will be present. The extraction method used is
dependant on the type of biological material that is to be analysed. A common
extraction method utilises a chelating-resin suspension. The resin binds to metal ions in
the solution, such as magnesium. The removal of magnesium inactivates nuclease
enzymes which would otherwise destroy the DNA. Following this extraction method,
the sample is added to a 5% solution of the resin, and boiled at 100 degrees Celsius.
Boiling the sample opens the cell membranes, destroys protein and denatures the DNA.
The mixture is then placed in a centrifuge. The resin and cellular debris are forced to the
bottom, and the supernatant liquid containing the single stranded DNA is removed from
the surface.31
In sexual assault cases, where the suspect’s DNA is in semen deposited in or on the
victim’s body, it is necessary to separate the suspect’s and victim’s DNA during the
extraction process. There are a number of methods used to achieve this. For example,
individual spermatozoa cells can be separated using magnetic particles coated with
antibodies that bind to proteins on the cells; or the biological material can be placed on
T9
slides, and the cells separated using micro-dissection techniques.
Human specific DNA quantitation is used to assess the quantity and quality of the
sample, and to exclude bacterial and other sources of DNA. A narrow concentration of
DNA is necessary to ensure that the assay is optimally conducted. For example, the
Profiler Plus kit used in Australia requires between 1 and 2.5 nanograms of DNA.
30 John Butler, Forensic DNA Typing (2005), 42-3. 31 Ibid.
32 K. Elliot et al, ‘Use o f Laser Micro-dissection Greatly Improves the Recovery o f DNA from Sperm on Microscope Slides’ (2003) 46 Forensic Science International 28-36.
