Title: Module 3: Admitting, Interpreting and Questioning Wildlife Forensic Evidence

Welcome to Module 3 of the Wildlife Forensic Science course.

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Welcome

[Image: Photo of an endangered cyad plant]

Welcome to Module 3: Admitting, Interpreting and Questioning Wildlife Forensic Evidence

The module enables the participants to achieve the following objectives:

- Explain the concepts of Chain of Custody, Validation and Quality Assurance, as they relate to wildlife forensic evidence.
- Assess the strengths and limitations of wildlife DNA forensic evidence.
- Appropriately question wildlife forensic evidence and avoid its misrepresentation in court.

Content for this resource was developed by TRACE Wildlife Forensics Network. Funding for the digitization of this content was provided through the USAID Combatting Wildlife Crime in Southern Africa Activity (VukaNow) in South Africa Contract No. 72067418C00005

The contents are the sole responsibility of the authors and do not necessarily reflect the views of USAID’s VukaNow Activity, USAID, or the United States Government.

Introduction

For forensic science to have a beneficial impact on wildlife law enforcement, it must be subject to reasonable testing and challenge by the legal profession.

Without sufficient scrutiny of the forensic methods used, standards will drop and the risks of miscarriages of justice increase. However, it is equally important that successful challenge of forensic evidence is based on realistic and substantive concerns, rather than spurious criticisms simply intended to undermine the prosecution. In this module, we look at how the delivery of forensic evidence can be supported by the prosecution and how different aspects of forensic evidence might be scrutinized by the legal profession to ensure that the evidence which is admitted to court is accurate, robust and appropriately presented.

GLOSSARY

This glossary includes key terms relating to wildlife forensics.

Click each term to reveal its definition.

Approach

A high-level description of the science being used – for example, DNA analysis.

Chain of custody

The documented process of secure evidence handling describing the location and person responsible for the evidence (evidence custodian) throughout its lifetime.

Deoxyribonucleic acid (DNA)

A long molecule found inside the cells of every animal and plant. A DNA molecule contains genetic code that holds instructions for cells to make proteins.

DNA barcoding

A standardized approach to comparing DNA sequences generated from an unknown specimen with a DNA sequence reference database in order to identify its species of origin.

DNA base pairs

Letters of the genetic code. There are four bases or "building blocks" in DNA: adenine (A), cytosine (C), guanine (G) and thymine (T). To form base pairs, adenine always pairs with thymine (A-T) and cytosine always pairs with guanine (C-G).

DNA marker

A specific individual section of DNA.

DNA profiling

A process where short regions of repeated DNA (1-6 bases long) are measured at markers around the genome and the results from multiple markers are combined to create a profile for the individual sample. This is also known as individualization.

DNA sequencing

A process where the genetic code is determined at a DNA marker.

Evidence security

A documented process for ensuring that evidence is kept demonstrably secure from crime scene to court room, through to subsequent storage or disposal.

Fallacy

A false belief or assertion.

Good Laboratory Practice (GLP)

General quality assurance (QA) requirements for laboratory testing.

Interpretation statement

The section of a forensic expert witness statement which goes beyond a factual account of the analyses performed and considers the expert opinion of the scientist.

Macroscopic

Visible using the naked eye.

Meta-data

In the context of forensic reference samples, meta-data refers to the non-genetic data that may be available regarding the sample, such as the time and location of sampling, information about the individual sampled, etc.

Method

The protocol being followed, for example, to generate a DNA sequence.

Method validation

A procedure to verify that an analytical method is suitable for its intended purpose and can generate robust, reliable data.

Microscopic

Requiring the use of a microscope to visualize.

Polymerase chain reaction (PCR) amplification

A process for making millions of copies of specific individual sections of DNA (known as DNA markers).

Protocol

The specific set of instructions used to describe a process.

Quality assurance (QA)

The management process that ensures that the delivery of a product or service, for example a laboratory test, is quality controlled.

Quality management system (QMS)

A documentation system that describes all of the steps involved in the delivery of a quality assured service or product.

Quantitative data

Data in the form of counts or numbers where each data point is represented by a numerical value.

Results statement

A statement of fact regarding the observed results of forensic analysis.

Technique

The specific approach being used, for example, DNA sequencing.

Scientific test

What the scientist is actually attempting to do; for example, generating a DNA sequence to identify the species.

First, we’ll look at case and witness preparation, and the crucial role it plays in the effective prosecution of wildlife crime.

Case and Witness Preparation

[Image: Person wearing gloves removing jar of evidence from brown evidence paper bag]

Prosecutors should be aware that, due to the relative novelty of wildlife forensic analysis in many countries, forensic scientists will have little or no experience of preparing a casefile and witness statements, or giving expert testimony in court. This last point, in particular, is critical; if the forensic expert witness is unable to communicate clearly to the court then it is unlikely that the evidence will have any impact at all.

Preparation is key.

PREPARING A CASEFILE

Forensic casework must be documented and authenticated throughout the analytical process. This documentation forms the basis of forensic reports and should be available to the court. A casefile should include details of:

Most wildlife forensic laboratory training delivered to new labs will include casefile preparation and generic reporting, but as the legal requirements for witness reports will vary from country to country, detailed instruction on casefile preparation and reporting is not normally provided and this creates a potential gap in the knowledge of new forensic science practitioners. It is in the prosecutor’s interest, therefore, to help the forensic scientists prepare for court.

CASE REVIEW

It is highly recommended to find an opportunity to conduct a casefile review involving the forensic scientist prior to a trial. Communication between prosecutors, investigators, and forensic scientists will identify any significant issues with the evidence and provide an opportunity to address these.

Click on the arrows to learn more on the questions that a casefile review should consider.

PRETRIAL HEARING

As with case review, with new types of forensic evidence, it can be very important to have the opportunity to explain the principles, processes and results to both the magistrates/judges and the defense counsel prior to the trial in court. This can be done by requesting a pretrial hearing, where there is greater scope for introducing the forensic methods and making the legal teams aware of the type of evidence that will be presented.

WITNESS PREPARATION

Inexperienced expert witnesses are very likely to make mistakes in court, usually through nervousness or, sometimes, through over-confidence. It is extremely helpful if prosecutors take the time to explain the court process and the role of the expert witness to the forensic scientists ahead of the trial.

If the expert witness feels comfortable and confident, they will likely provide useful testimony. It is also good to explain to the forensic scientist the types of questions that they may be asked as the expert witness under cross-examination.

Please remember that forensic scientists are required to be impartial, unbiased reporters of their analytical work. They are not seeking to support the prosecution’s case.

Sometimes this means that their evidence may not be entirely what the prosecution wants to hear. This is another reason to hold a casefile review, rather than be surprised in court.

The casefile review and pretrial hearing help prosecutors ensure that the forensic evidence presented in court is not only admissible but is also seen as credible and reliable.

In the next lesson, we will identify and explore potential challenges to using forensic evidence at trial.

Potential Challenges at Trial

[Image: A photo of a wooden judge's gavel resting on the block]

We now turn to the trial itself and issues affecting the admissibility and interpretation of wildlife forensic evidence. This section is relevant to judges and magistrates who may want to understand common issues with wildlife forensic evidence. Equally, a competent prosecutor should be aware of these points in order to ensure that the evidence is produced and presented with as few question marks as possible.

ADMITTING EVIDENCE

Irrespective of the actual scientific test used, the following aspects of the forensic analysis should be considered as possible points of challenge:

Establishing the witness as an expert in the field is important and should be performed by the prosecutor at the beginning of testimony. Educational background, training courses, and forensic society membership should all be elicited through initial questions.

Currently, there is very little opportunity for wildlife forensic scientists to become certified, especially if they have little or no previous casework experience. The certification scheme of the Society for Wildlife Forensic Sciences (SWFS) will certify practitioners but not until they have completed at least five cases, which creates a challenge for new laboratories and staff.

For more information, please visit the SWFS website.

In some cases, the laboratory service provider is in a different country to where the trial occurs. This is especially true where there is no national capacity for wildlife forensic analysis in the country of the trial. To ensure that evidence produced by such labs is admitted, it is important to understand and clearly document the way in which the lab performed the analyses. Additionally, the prosecution should be aware of this before trial so that they can make decisions about appropriate witnesses and witness statements, and to anticipate challenges in this type of situation. This is another area where pretrial preparation and discussion is key to an effective prosecution.

As we discussed in Module 2, Lesson 4, gaining accreditation is not easy for wildlife forensics laboratories, due to the costs of accreditation and the lack of qualified assessors. Accreditation is always preferable but is not mandatory for evidence admissibility. What is more important is that the laboratory is aware of the relevant standards (for example, ISO17025 and SWFS) and is able to demonstrate and discuss its Quality Management System (QMS). It is possible for a QMS to be in compliance with external standards, without being formally accredited.

As with the issue of individual competency, it is advisable to discuss laboratory standards during examination-in-chief, so that the scientist is given the opportunity to explain why they are not accredited and why it is not critically important.

Evidential security is the favorite point of attack for the defense, especially when evidence has been transferred between agencies, which will happen with forensic analysis. Forensic scientists are likely to use “tamper-evident” systems for sample storage at the laboratories. Tamper-evident systems are not necessarily physically secure, but demonstrate whether evidence has been tampered with, or whether it has remained secure. Ensure that you are familiar with this type of evidence security.

It is important for prosecutors to keep these factors in mind when preparing to present forensic evidence in court, and equally vital for the judiciary to interrogate the admissibility of evidence based on these factors.

QUESTIONING THE EVIDENCE

Challenges to the actual wildlife forensic evidence may be less likely, but it is still very important to be aware of common issues that affect the acceptance of analytical findings by the court.

The court and/or the defense may question the laboratory techniques, their validation and/or the interpretation of results.

The following section will cover these elements in more depth and the kinds of issues concerning the forensic evidence that should be considered.

TECHNIQUES

Considerations:

- Although relatively simple to perform, the technique must be carried out by someone with training and experience, following a standardized protocol.
- It may not be possible to apply the technique to worked ivory products.
- The technique cannot differentiate species of elephant (for example, African from Asian).

Considerations:

- The result sequence should be compared against that from known reference material.
- Due to sequence variation within species, the DNA sequence of an evidence item may differ to the reference sequence of a species (i.e. the sequence match is less than 100%), without excluding it from belonging to that species. In such situations, the relative level of difference between the evidence sequence and different candidate reference sequences must be considered.
- The overall length of the sequence should be reported as well as the percentage sequence similarity to the reference sequences.
- While DNA sequence data do not yet exist for every species, data do exist for most mammals, enabling identification of most species subject to illegal killing or trade.

Considerations:

- The strength of evidence associated with matching DNA profiles is associated with the chance of observing another individual in the population with the same profile. The smaller the chance, the stronger the evidence for a true match.
- Close relatives have a much higher chance of sharing DNA profiles than two unrelated individuals.

During the trial, questions may also arise regarding method validation and quality assurance (QA).

VALIDATION AND QUALITY ASSURANCE

QA is usually implemented through a Quality Management System (QMS) that consists of a documented record of the laboratory systems, protocols, and control processes. A QMS may be accredited against an internationally recognized standard (for example, ISO17025).

The level of confidence in any laboratory analytical result relates to the degree of QA surrounding the production of the data. The QA concept is fundamental to the performance of any test where the results are later relied upon by a third party, such as the court.

Laboratory QA standards are highly technical and law enforcement agencies may have difficulty in determining and selecting a suitable laboratory to complete forensic analysis of wildlife specimens. This can result in difficulties in court when assessing the reliability of evidence. Without a level of knowledge concerning QA, there is a risk that enforcement agencies will commission analysis from laboratories that are not operating to sufficient standards. Similarly, it is not easy for the courts to make an informed decision over the admissibility of evidence without knowledge of good practice.

At the very least, laboratories conducting wildlife forensic testing should have implemented a QMS and casework documentation system, available for review by relevant investigation agencies and the court. Furthermore, this QMS should be subject to internal auditing and external assessment by an independent third party.

Finally, the interpretation of results in forensic reports may be questioned during a trial.

INTERPRETATION

Forensic reports are likely to include a result statement followed by an interpretation statement.

Click each term to review each type of statement.

Results statement

The results statement is a statement of fact regarding the observed results. For example:

“A DNA sequence was generated from the evidence item and observed to be a 100% match over 350 base pairs to an existing reference sequence from a lion, Panthera leo.”

There is no dispute over this statement, but there may be disagreement about what it means in the context of the evidence identification.

Interpretation statement

The interpretation statement is important as it allows the forensic scientist to consider the evidence, given both the proposition of the prosecution and the proposition of the defense. Failure to do this could be considered to demonstrate bias in favor of the prosecution.

The advantage of using an interpretation statement is that the forensic scientist can comment on how likely it is to have observed the result, given the two competing propositions. For quantitative data with probabilities, this is usually presented as a likelihood ratio, referring to relative likelihoods of the two propositions.

STRENGTH OF EVIDENCE

Forensic scientists are often trained to comment on the strength of the evidence to help the court understand and interpret the results more easily. A written scale of support for one proposition over another may use the following terms:

Let’s look at two statements: one expressing a forensic scientist’s extremely strong support, and one expressing moderate support for observing two results relating to the same piece of evidence.

These two statements indicate that the strength of evidence for the species identification is greater than the strength of evidence for matching the horn to an individual rhinoceros.

You will note that the wording above describes the strength of the evidence in terms of its support for one proposition relative to another. Neither of these statements directly assesses the guilt or innocence of the suspect. This is a very important distinction. The role of the forensic scientist is to evaluate the likelihood of the evidence, given the two propositions being considered, rather than the likelihood of guilt. That is to say, the evaluation of the evidence is conditional on the prosecution and defence propositions.

PROSECUTOR'S FALLACY

A common issue when commenting on the strength of the evidence under examination-in-chief, is that the prosecutor will lead the witness towards answering a question relating to the likelihood of the suspect’s guilt.

This is technically termed transposing the conditional and is commonly known as the “prosecutor’s fallacy”.

The prosecutor’s fallacy is a mis-statement of a probability as a result of a misunderstanding of conditional probability. This typically results in the court being incorrectly informed about the likely guilt of the suspect.

In order to reduce the risk of bias, forensic scientists are trained to comment on the evidence, rather than to make definitive statements about the case. Both prosecutors and the judiciary need to be aware of this issue to avoid compromising the use of forensic evidence.

For example, consider a DNA profile match between a rhino horn and carcass. The odds of seeing matching profiles if the horn did not come from the carcass are 1 in 1 million.

How should this finding be stated? Click on the correct interpretation statement.

Multiple Choice

Q: Which of the following is the appropriate interpretation statement?
- “It is one million times more likely to see matching profiles if the horn came from this rhino carcass rather than another rhino in the population.” (correct) (Correct! This is the appropriate interpretation statement concerning the findings. In this statement, the probability refers to observing the evidence. The statement is conditional on the probability of the evidence.) (if not chosen: This is the appropriate interpretation statement concerning the findings. In this statement, the probability refers to observing the evidence. The statement is conditional on the probability of the evidence.)
- “There’s a one in a million chance that the horn came from a different rhinoceros.” (This is incorrect. This is a statement about the probability of the prosecutor’s proposition, not the evidence. Quite often, the prosecutor will inadvertently transpose the conditional.) (if not chosen: This is a statement about the probability of the prosecutor’s proposition, not the evidence. Quite often, the prosecutor will inadvertently transpose the conditional.)

The prosecutor’s fallacy is quite a technical issue but is highly relevant to all forms of forensic statistics, particularly genetic data.

Conclusion

Well done on completing the final module of this course!

Forensic evidence can support casework, provide intelligence and vitally, facilitate successful prosecutions. To ensure the best use of this powerful tool, it is important to understand that:

- Forensic science runs from crime scene to courtroom;
- Scientific approaches are driven by investigative questions; and
- Forensic science requires effective coordination amongst multiple agencies.

To complete this module, advance to the Summary page, and click Submit report.

For more information on key considerations when dealing with forensic evidence, download the appendix here.