DNA EXPERT

Authoritative DNA expert reports and oral testimony

A preliminary DNA expert review can be a useful step in assessing the broad strengths and weaknesses of a particular matter. This process can also identify documentary and any further evidence requirements.

Rigorous interrogation of the evidence will uncover underlying issues and determine the most appropriate pathway towards reviewing and reporting the matter.

Certain complex matters benefit from a draft DNA expert report, which can open areas for discussion with Counsel, and potentially allow for defence to approach the prosecution.

Following a thorough evaluation of the evidence, a DNA expert report will be issued in accordance with the expert witness code of conduct. The report will be suitable for submission in evidence.

Preparations with Counsel are often conducted, such that the probative value of the evidence is weighed effectively and persuasively at Voir Dire, should such a hearing be required.

Extensive preparations are generally conducted in anticipation of substantive hearing. Which may include cross examination and evidence in chief scenarios specific to the matter .

DNA EXPERT

The justice system is substantially reliant upon DNA expert evidence to assist in the determination of serious criminal matters.

DNA expert analysis, interpretation and review, relies upon a thorough and stringent application of current scientific theory, statistics and expertise.

The utilisation of DNA expert evidence to inculpate or exculpate in the context of a serious criminal matter, warrants the utmost precision and attention to every detail.

Our rigorous approach, is steeped in experience from the infancy of DNA analysis in the early 2000’s, spanning literally thousands of DNA criminal matters.

The leading of a DNA expert in defence, will inherently rely upon the authority of the expert opinion. It is the formulation, underpinning, credibility and ultimate reliability of this opinion, which can turn a matter regarding contested DNA evidence.

The justice system is substantially reliant upon DNA expert evidence to assist in the determination of serious criminal matters.

DNA expert analysis, interpretation and review, relies upon a thorough and stringent application of current scientific theory, statistics and expertise.

The utilisation of DNA expert evidence to inculpate or exculpate in the context of a serious criminal matter, warrants the utmost precision and attention to every detail.

Our rigorous approach, is steeped in experience from the infancy of DNA analysis in the early 2000’s, spanning literally thousands of DNA criminal matters.

The leading of a DNA expert in defence, will inherently rely upon the authority of the expert opinion. It is the formulation, underpinning, credibility and ultimate reliability of this opinion, which can turn a matter regarding contested DNA evidence.

False inclusion

A DNA false inclusion can occur with any probabilistic genotyping software used to interpret mixed DNA profiles.
A false inclusion is an inclusionary result, when that individual has in fact not contributed to the profile.
One empirical STRmix study which simulated 300,000 mixed DNA profiles, showed that false inclusions occurred in 2900 of those cases.
A key indicator that flags a potential false inclusion is a low likelihood ratio, as are complex profiles and allele sharing.
Subjective actions within the laboratory can be of notable significance with false inclusions, including the number of contributors assigned, and formulation of propositions.

DNA TRANSFER

DNA is highly transient and can be readily transferred from one surface to another. DNA transfer evidence may not in all circumstance prove probative.
Expert DNA analysis will seek to evaluate the DNA – TPPR (transfer, persistence, prevalence, recovery), which may be impacted upon my multiple variables such as substrate, porosity, contact pressure, applied friction or shedding status, to name a few.
Activity Level Reporting (ALR), is a statistical assessment that seeks to determine the probability of obtaining the DNA profile, given specific hypotheses.
ALR may be applied in certain matters where it is scientifically robust to do so.

MIXED DNA PROFILES

The advancement of DNA technology over recent decades has led to a dramatic increase in testing sensitivity. This increased sensitivity means that the majority of DNA profiles before the courts, represent a mixture of contributors.
A mixed DNA profile is inherently more complex to assess than in a single source profile.
In general terms, the greater the number of contributors, and the lessor the amount of DNA, the more complex the mixed DNA profile is to interpret.
When analysing a mixed DNA profile, the possibility of a familial co-contributor needs to be considered, and ethnicity may be a factor for consideration, as with all DNA profile interpretation.

DNA CONTAMINATION

DNA contamination regularly occurs during crime scene investigation, laboratory procedures, or as consequence of background DNA.
The significance of contamination upon the matter can vary greatly.
Scrutinisation of body worn camera footage, crime scene sampling methods, batch numbers, quality control records, exhibits order, quality management incident reports, sample batch records and re analysis records, are some of the pathways which may provide further information as to potential for contamination within a specific matter.
 Rigorous interrogation of the evidence is critical in the assessment of DNA contamination.

DNA TESTING

Testing conducted by a government laboratory and served in evidence, is not in all circumstances robust.  Roebuck Forensics is equipped to advise on the reliability of specific evidence as served, and determine if independent testing is required, in order to achieve probative evidence.
In the advent that testing is required, we are able to conduct retesting of existing samples, or resampling items for testing. Our DNA testing methods and procedures are strictly conducted to preserve the chain of custody, and accord with industry best practice, in order to serve evidence that is reliable and informative as to the facts before the courts.

CRIME SCENE EXAMINATION

Crime scene examination process can lead to problematic evidence that fails an evidentiary test. Our thorough review process considers the veracity of the evidence, and further seeks to determine how crime scene examination contributed to the evidentiary value.
This information can of itself contribute with significance towards the outcome of a matter.
We hold considerable expertise in crime scene examination, and can advise when this process is of utility.
False inclusion

False inclusion

A DNA false inclusion can occur with any probabilistic genotyping software used to interpret mixed DNA profiles.
A false inclusion is an inclusionary result, when that individual has in fact not contributed to the profile.
One empirical STRmix study which simulated 300,000 mixed DNA profiles, showed that false inclusions occurred in 2900 of those cases.
A key indicator that flags a potential false inclusion is a low likelihood ratio, as are complex profiles and allele sharing.
Subjective actions within the laboratory can be of notable significance with false inclusions, including the number of contributors assigned, and formulation of propositions.
TRANSFER

DNA TRANSFER

DNA is highly transient and can be readily transferred from one surface to another. DNA transfer evidence may not in all circumstance prove probative.
Expert DNA analysis will seek to evaluate the DNA – TPPR (transfer, persistence, prevalence, recovery), which may be impacted upon my multiple variables such as substrate, porosity, contact pressure, applied friction or shedding status, to name a few.
Activity Level Reporting (ALR), is a statistical assessment that seeks to determine the probability of obtaining the DNA profile, given specific hypotheses.
ALR may be applied in certain matters where it is scientifically robust to do so.
MIXED PROFILES

MIXED DNA PROFILES

The advancement of DNA technology over recent decades has led to a dramatic increase in testing sensitivity. This increased sensitivity means that the majority of DNA profiles before the courts, represent a mixture of contributors.
A mixed DNA profile is inherently more complex to assess than in a single source profile.
In general terms, the greater the number of contributors, and the lessor the amount of DNA, the more complex the mixed DNA profile is to interpret.
When analysing a mixed DNA profile, the possibility of a familial co-contributor needs to be considered, and ethnicity may be a factor for consideration, as with all DNA profile interpretation.
Contamination

DNA CONTAMINATION

DNA contamination regularly occurs during crime scene investigation, laboratory procedures, or as consequence of background DNA.
The significance of contamination upon the matter can vary greatly.
Scrutinisation of body worn camera footage, crime scene sampling methods, batch numbers, quality control records, exhibits order, quality management incident reports, sample batch records and re analysis records, are some of the pathways which may provide further information as to potential for contamination within a specific matter.
 Rigorous interrogation of the evidence is critical in the assessment of DNA contamination.
Testing

DNA TESTING

Testing conducted by a government laboratory and served in evidence, is not in all circumstances robust.  Roebuck Forensics is equipped to advise on the reliability of specific evidence as served, and determine if independent testing is required, in order to achieve probative evidence.
In the advent that testing is required, we are able to conduct retesting of existing samples, or resampling items for testing. Our DNA testing methods and procedures are strictly conducted to preserve the chain of custody, and accord with industry best practice, in order to serve evidence that is reliable and informative as to the facts before the courts.
CRIME SCENE

CRIME SCENE EXAMINATION

Crime scene examination process can lead to problematic evidence that fails an evidentiary test. Our thorough review process considers the veracity of the evidence, and further seeks to determine how crime scene examination contributed to the evidentiary value.
This information can of itself contribute with significance towards the outcome of a matter.
We hold considerable expertise in crime scene examination, and can advise when this process is of utility.

DNA QUESTIONS

DNA Likelihood Ratio

The likelihood ratio is the accepted method of evaluating DNA evidence. If the LR is 100 billion, the results are 100 billion times more likely if the crime scene DNA comes from the defendant than from a different person.

Is DNA ever a 100% match?

Forensic DNA testing only analyses a very small portion of the DNA molecule. Therefore, when a person’s reference DNA profile matches a crime scene sample, there is a possibility that other unknown and family members may match.

What is a ‘good’ likelihood ratio?

The verbal likelihood ratio can range from ‘weak’ to ‘extremely strong’. In Australia, the upper end of the numerical scale is capped at 100 billion.
Scientific research has shown that false inclusions can generate likelihood ratios up 750 000.

Can the DNA likelihood ratio be wrong?

The DNA likelihood ratio can be wrong by false inclusion or the numerical likelihood ratio is scientifically invalid.
In Australia, the numerical likelihood ratio is produced using STRmix, with TrueAllele and EuroForMix used also.

DNA and population size

A likelihood ratio of 100 billion may falsely infer that no one else in the world could match the DNA profile. Rarely do likelihood ratios consider related individuals and mixed DNA profiles cannot be reduced to such simple logic.

DNA Transfer

DNA is highly transient and can be readily deposited, picked up and re-deposited. The chain of events leading up to the ultimate deposition are the subject of forensic consideration particularly when seeking to answer ‘how’ and to a lesser extent ‘when’.

How to prove DNA transfer

It is not possible to conclusively prove that DNA was deposited directly or indirectly (transfer). The consideration of DNA transfer must be conducted scientifically by way of Activity Level Reporting and cannot be a mere speculation such as ‘more likely’.

What is secondary DNA transfer?

Secondary DNA transfer denotes a transfer scenario with one intermediary surface. Secondary transfer has now been subsumed within the term indirect DNA transfer, which accommodates a broader number of potential scenarios

What is tertiary DNA transfer?

Tertiary DNA transfer refers to indirect transfer that involves two intermediary contact points, leading up to the ultimate deposition.

What is DNA time since deposition ?

It is not currently possible to age trace DNA deposition. There are known factors of degradation, which are being applied within scientific studies in an effort to establish a time since deposition understanding.

How long does DNA last on a surface?

DNA deposited onto protected surfaces is quite stable and may remain for many years, so much so that background DNA within a built environment is of significant forensic consideration. Environmental factors such as heat and UV light will contribute to DNA breakdown.

DNA Activity Level Reporting

DNA Activity Level Reporting is an often highly complex scientific process that evaluates activity such as ‘how’ or ‘when’ the DNA was deposited. The process typically considers the prosecution and defence hypotheses and must produce a numerical ratio which is supported by evidenced data.

Is it valid to say DNA transfer ‘more likely’ ?

DNA transfer ‘more likely’ is commonly and invalidly used in support of ‘how’ the DNA was deposited.
“how” trace DNA was deposited must only be evidenced through the process of scientific Activity Level Reporting.

How reliable is touch DNA?

Touch DNA is a scientifically redundant term which may be erroneously used to denote trace DNA. Trace DNA is cellular DNA which cannot be attributed to a biological fluid.

How was the DNA deposited?

The courts are critically seeking science to answer how was the DNA deposited. It is not possible to determine this merely from reviewing a DNA profile. An activity level assessment of the evidence may assist in assigning a likelihood ratio that evaluates two versions of events supplied.

When was the DNA deposited?

It is not possible to scientifically determine when DNA was deposited. Furthermore, it should never be assumed that DNA contained within a mixed DNA profile was all deposited at the same time.

DNA - Sexual Assault

DNA is forensically relied upon in support of physical sexual assault allegations. Scientifically, the areas of consideration are trace DNA and attribution to a biological fluid such as semen, saliva or blood.

How long does sperm last in the vagina?

Sperm can last in the vagina for a matter of hours and for up to 7 days. Sperm cells are a rich source of DNA. The time since ejaculation, specific location, vaginal environment, and mechanical actions following deposition (such as bathing and toileting) can all impact upon the rate at which the DNA rich cells are voided or degraded.

How long do sperm last outside the body?

Sperm can survive for only a matter of hours outside the body, however this does not relate to the question of raising a DNA profile.

What does sperm fraction mean?

In order to attribute DNA to sperm, the cells are first separated from the other cells. The resultant sperm fraction is not absolute and may contain non sperm cell contamination. We often see female DNA within the sperm fraction.

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Difference between YSTR and standard DNA testing?

YSTR testing targets short tandem repeats (STR’s) on the Y chromosome (male) only. YSTR testing is typically used in sexual assault scenarios where there is low DNA or the standard DNA testing was found to be uninterpretable.
YSTR DNA results will inherently match many more persons within the population than a standard DNA testing result.

DNA Report

How long does a preliminary DNA review take?

A preliminary review involving the biological casefile will commonly take between 2 and 4 hours to complete.
This process can be of great utility when seeking to understand the relative strength of the DNA evidence.

Can the DNA evidence be reviewed from the prosecution DNA report?

The prosecution DNA report provides limited information to the reader.
In order to review the matter in specific detail, the laboratory casefile will be required.

What is the scale of support?

The scale of support is a way of translating the numerical likelihood ratio into words. Such verbal qualifiers must be derived from and be in specific reference to the numerical likelihood ratio, and cannot be a mere stand alone speculation.

What is a DNA adventitious match?

An adventitious match is one where the person is not the true donor of the DNA. This may arise when the DNA profile contains information from a limited number of loci that are insufficient to distinguish the profiles of two different individuals

What does DNA profile uninterpretable mean?

This refers to inability to interpret or use the DNA profiling results for comparisons due to poor or limited data quality. Relevantly, it does not mean that further testing will not, or cannot be conducted successfully.

Does ‘cannot exclude’ mean the same as match?

The phrase cannot exclude is frequently encountered in DNA reports, which infers inclusion.
Should this inclusionary result be absent of a statistical likelihood it is inadmissible.

DNA - Facts

Can two people have the same DNA?

Whilst DNA is unique to the individual, two DNA profiles of two different people may appear the same.  Forensic DNA analysis looks at only a very small portion of the DNA molecule, and therefore it is possible for two or more individuals in the population to share the same DNA profile.

How long does DNA testing take?

Whilst a DNA profile can technically be obtained in as little as a few hours, testing in Australian criminal matters can often take a matter of weeks and months.

Do family members share DNA?

DNA is inherited from your biological mother and father, therefore you will share DNA with you relatives.  Parent and child share 50% of their DNA as do siblings, grandparents share 25% of their DNA with their grandchildren, and cousins share 12.5%. Identical twins have identical DNA and therefore an identical DNA profile.

Do blood transfusions change your DNA?

When a person receives a blood transfusion, their DNA will not be altered.  However, in most people, it is possible to detect a very small amount of the donor’s DNA in the recipient’s blood for a few days after the transfusion.

Does DNA determine appearance?

Forensic DNA analysis does not target a person’s appearance, and does not contribute answers on hair and eye colour for example..  These regions of the DNA molecule are referred to as non-coding, or junk DNA.

What is the National DNA database?

Many countries maintain a national DNA database comprising of DNA profiles collected from crime scenes, convicted offenders, suspects, volunteers, items belonging to missing persons and unknown human remains.

The Australian Criminal Investigation DNA Database (NCIDD) holds more than 1.6 million DNA profiles.

DNA - Court

Will more DNA evidence be served by prosecution?

Most prosecutions proceed in a piece meal fashion regarding DNA. Typically the initial material is quite scant and does not necessarily go entirely to the specific scientific substance of the matter. Unless requested prior, further detailed information is generally served, which is not uncommonly on the steps.

Should I request further scientific evidence?

The question of requesting material is a fraught one, and should be evaluated very carefully regarding the scientific merits of the specific matter.

Will DNA transfer evidence be excluded at Voir Dire?

We regularly proffer expert opinion on DNA transfer evidence, which is subsequently determined more prejudicial than probative by the courts and excluded. DNA transfer evidence should always be considered on a matter specific basis, rather than with superficial and generalised speculation.

Can DNA evidence alone support the prosecution?

In theory DNA evidence should not be relied upon solely, however certain matters present with little else of substance. DNA evidence is never absolute, meaning great care should be taken to present the true evidentiary weight of the scientific evidence.

Can I get Legal Aid funding?

We are regularly instructed in matters which are legal aid funded.

DNA - Laboratory

What causes DNA contamination?

DNA contamination involves the introduction of foreign DNA into a sample.  It can occur at many stages during the crime scene examination and within the laboratory.

How to determine DNA contamination?

To consider DNA contamination we would scrutinise batch records, control sample records, contamination reports and evaluate the specific makeup of the DNA profile.

Can DNA samples be mixed up?

A thorough review of the continuity relating to a DNA sample can identify whether two samples have been mixed up.

Do DNA samples degrade over time?

DNA degradation can increase with factors such as exposure to UV light, heat, and microbial activity.  Degradation of samples is significantly reduced by freezing of samples, however it is not entirely eliminated as the thawing process can advance degradation.

DNA - Terms

DNA

Deoxyribonucleic acid (DNA) is a molecule inherited from biological parents, that determines a person characteristics. It carries genetic instructions for the development, functioning, growth and reproduction of all known organisms, and is often referred to as the blue print for life.

DNA profiling

DNA profiling is the comparison of a POI (person of interest) profile against the DNA evidence recovered from a crime scene.

Genotype

Genotype is the genetic constitution of an organism, as distinguished from its physical appearance (its phenotype). In forensic DNA analysis the genotype of an individual is represented by their DNA profile.

Short tandem repeats (STR)

Short tandem repeats are sections of the DNA molecule where multiple copies of an identical DNA sequence are present, with the number of times the sequence repeats varying among individuals.

Y Chromosome tandem repeats (YSTR)

YSTR broadly relates to the Y chromosome, making it a useful method of determining male DNA, as distinct from female DNA.

Chromosome

Chromosome is the structure by which hereditary information is physically transmitted from one generation to the next. The human genome consists of 46 chromosomes, arranged in pairs.

Locus

Locus is the physical location of the gene on a region of a chromosome. Pl loci.

Allele

Allele is a version of a genetic sequence at a particular location in the genome. In forensic DNA analysis an allele represents the number of repeat units in the short tandem repeat (STR) typically.

Electropherogram

Electropherogram is a graphical representation of the DNA profile. Referred to as an ‘EPG’, it displays the alleles, and the size of the DNA fragments.

Mixed DNA profile

A mixed DNA profile contains DNA from more than one individual. Mixed DNA profiles are inherently more complex to interpret than single source DNA profiles which originate from only one individual.

STRmix

Software which combines biological modelling and mathematical processes to interpret a wide range of complex DNA profiles.

PowerPlex 21

Currently in use by the majority of Australian and New Zealand government owned forensic laboratories. This test targets 21 areas of the DNA molecule and is highly discriminating.

Globalfiler

Currently in use by some Australian government forensic laboratories. This test targets 24 areas of the DNA molecule and is highly discriminating.

Profiler Plus

Previous used by all Australian and New Zealand government forensic laboratories until approximately 2010, when it was superseded by the more discriminating PowerPlex 21 and Globalfiler tests. ProfilerPlus targets 10 areas on the DNA molecule.

Y Filer Plus

A specialised test which targets DNA on the Y Chromosome, in males only. This test targets 27 areas of the DNA molecule and is highly discriminating.

Y Filer

A specialised test which targets DNA on the Y Chromosome, in males only. This test targets 17 areas of the DNA molecule and is highly discriminating.

DNA extraction

DNA extraction is the process of extracting the DNA from the cell nucleus.

DNA quantification

DNA quantification is the measurement of the total amount of DNA within the sample. Some methods will also measure the ratio of male to female DNA; as well as the degredation within the sample.

DNA amplification

DNA amplification is the process of making millions of copies of the DNA contained within the sample. It is conducted using the polymerase chain reaction (PCR).

DNA capillary electrophoresis

DNA capillary electrophoresis is used to separate out the DNA fragments based on their size, to enable the number of short tandem repeats present to be measured.

Genemapper

Genemapper is a software program used to designate peaks in electropherograms by sizing and makes allele calls through size comparisons to an allelic ladder.

Electropherogram (EPG)

An electropherogram is a chart used in DNA profiling which shows the peaks in the DNA fragments.

DNA Artefacts

DNA profiling often results in non-allelic products termed artefacts.
DNA artefacts occur commonly and require a skilled analyst to interpret. Artefacts may complicate interpretation of a DNA profile, as they are not always readily distinguishable from actual allelic data.

Negative controls

Negative controls in DNA analysis have no sample added to them. If the negative control does not return a DNA profile, then this demonstrates that contamination has not been introduced into the assay during the testing process via reagents, disposables, or handling errors.

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