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Article for The Academy of Experts

The following article about forensic DNA reports and limitations of Streamlined Forensic Reports (SFR) was written by Jo Millington for The Academy of Experts (TEDR)

Forensic DNA Reports

There is increasing pressure across the Criminal Justice System to deliver forensic science more quickly and for less money. The faster/cheaper philosophy is epitomised in the Streamlined Forensic Reporting (SFR) process. This approach was introduced by the CPS to ‘reduce unnecessary costs, bureaucracy and delays in the criminal justice system’, and ‘to ensure that the key forensic evidence that the prosecution intend to rely on is presented in the shortest and clearest way so as to achieve early agreement on forensic issues and to identify contested issues’. It is implied that the SFR ‘report’ will outline the scientific evidence in such a way that the reader will understand the strengths and limitations of the scientific findings in context of their case, and that it will be upgraded into a court report, which addresses the key issues and satisfies the Criminal Procedures Rules, as and when necessary. Yet, on a regular basis, we deal with cases on behalf of the Defence, in particular, where the DNA evidence has only been conveyed in an abbreviated form, with no opinion from a Crown scientist regarding what the DNA match could mean in the context of the case circumstances. This introduces risk into the Criminal Justice System.

As an example let’s consider the ‘DNA Stage 1 SFR’. This document will typically provide the reader with information about the author (sometimes this can be an ethereal department or unit), details of the case (such as location and dates) and a summary of the DNA result (the match generated between a crime sample and a named individual). It may also provide information to indicate if the profiles have been generated using the same DNA technology, or if the crime profile comprises a mixture of DNA, although these details might not be readily apparent to the non-scientific reader.

Having reviewed a number of police interviews, it is not unreasonable to then consider that the defendant might be presented with the SFR and asked to offer an explanation as to how ‘their’ DNA came to be present at a crime scene. It’s probably like being asked for your pin number when you have been using contactless payments for the last few months. Eventually you might recall your pin, but consider whether you could readily explain, if asked, where your DNA might be. We’re not talking about great lumps of DNA, we’re talking about invisible to the naked eye, bits of you that you may have left purposefully or unintentionally on things. It also relates to DNA that may have been further transferred by others, without your permission. However, if an explanation is provided it is critical that the DNA match is evaluated in light of it, alongside any proposition that has been put forward by the Prosecution.

The usefulness of DNA evidence in the context of an investigation is only fully realised once the individual results have been evaluated in light of the case circumstances. Yet cases continue to progress, even to trial, on the basis of the initial DNA match, even though it is quite clear on the SFR Stage 1 template that the report is not intended for use at court.

The limitations of DNA are to some extent rooted in its success. The boom in DNA technology, which evolved in response to the requirement to be faster and cheaper, led to the development of a rich portfolio of specialist and more sensitive techniques. Tools are now available that can generate DNA profiles from minute traces of biological material, whether the DNA is related to the investigation or not. Scientists no longer need a detectable body fluid or an observable stain for analysis because the standard, everyday, techniques have the ability to develop information from speculative (invisible) samples; and if they fail, specialist tests can be applied to clean-up, concentrate and optimise the recovery of DNA from the most inhospitable of samples.

If, or inevitably when, the resulting profile comprises a mixture of DNA, it is often possible to resolve it into the profiles of the individual contributors and/or simplify it using information that is specific to the case. This is called ‘conditioning’, disentangling the mixed profile on the basis of information relating to DNA that is expected to be there - such as DNA from the donor of the sample. Where mixed profiles continue to be beyond the capacity of standard statistical programs, specialist probabilistic methods can be employed (e.g. likeLTD or STRMix) to de-convolute the most complex of mixtures (up to a point).

Before the widespread introduction of these specialist approaches, scientists were permitted to provide a ‘subjective assessment’ of the mixed DNA results that standard methods could not resolve. This involved, essentially, counting the number of DNA components in a crime profile that matched components in an individual’s reference profile, and conveying the extent of the match numerically or in the form of a verbal strength of support. This practice, which was only ever intended to be an interim measure, introduced a level of greyness in the evaluation of DNA findings that was difficult to standardise. ‘Qualitative evaluations’ are known to be susceptible to cognitive bias and have the potential to be prejudicial, but it was implied that the practice was sufficiently calibrated that it could provide a robust indicator in terms of whether or not an individual may have contributed DNA to a sample. In fact it was scientifically impossible to say one way or the other, simply because the opinion existed in an area that was beyond the scope of any quantitative or empirical data. This practice is no longer supported [1] (or necessary) given the introduction of accredited specialist software.

Subjective opinion hasn’t been completely outlawed, but when a non-numerical opinion is presented, for example in an intelligence report or as a holding position until the appropriate statistical assessment can be completed, it is imperative that the provisional nature of the evaluation is made clear. It is not an evidential opinion and it would be unwise to consider it as such. Therefore if the report does not include a statistical assessment of the result, a request should be made for that work to be done before the evidential status of the DNA result is accepted.

The restricted format of the SFR does not accommodate a freestyle presentation of the complexities of DNA mixture interpretation and in some cases an abbreviated form of witness statement might be issued. Abbreviated formats allow scientists to provide a summary of the evidence, whilst embellishing on the nature of the DNA result and its evaluation. It is shortened, typically, by removing details about the qualifications of the author, case and continuity information and technical detail. Now, more than ever, the decision to exclude an outline of an expert’s credentials and competencies in any report that is intended to be used by the court would seem misplaced. Even if it does mean that brevity will reduce the overall cost.

It is not unusual for abbreviated reports to focus on the make-up of the DNA result and any possible matches. They may include phrases to emphasise that the expert has not yet dealt with a full interpretation of the findings but if this was required, that a full statement should be requested through the appropriate Forensic Submissions Unit. It is questionable whether these phrases are recognised as calls to action, or if the consequence of not acting on them is fully appreciated. In practice these caveats are outlining that if a DNA result (for example) is likely to have a leading role in any investigation, a full interpretation must be requested. Interpretation of DNA is multi-faceted. It can involve an assessment of whether the DNA can be attributed to a particular body fluid. For example, if blood was tested, is there confidence that the DNA came from blood? It can also involve a consideration of what the DNA findings might mean in the context of the allegations that have been made. For example do the DNA findings help in determining how or when the DNA may have been deposited? This is an area of forensic thinking commonly referred to as ‘transfer and persistence’ and there are a number of research publications emerging on this topic.

As a consequence of how ‘staged reporting’ has evolved, the way in which scientific findings, a DNA result for example, are conveyed can change significantly depending on when the evidence is introduced into the CJS process. Whether it has been fully evaluated in context with the case circumstances, or not, or whether the results have been conveyed in a particular type of report can fundamentally impact the evidential significance of the result.

SFRs and abbreviated reports might be popular because they are thought to accelerate the crime scene to court process, but if the findings on which the case is built can be neutralised once a full interpretation is conducted, it is arguable whether they are fit for purpose. If the findings were evaluated at the outset, it is possible that the investigation strategy, or efforts in building a charge, or in advising a client could be more effectively managed.

As a general rule our advice is that unless the DNA findings have been specifically evaluated in light of the case circumstances, including the scenarios that have been presented by the Prosecution and Defence, their potential evidential significance should be considered as undefined.

If you are dealing with a case in which these factors apply, please give us a call. We always offer free advice and we are able to provide quotes for Legal Aid purposes if necessary. We have a combined experience of over 40 years, working in the arena of forensic evaluation, including DNA and body fluid interpretation, and we can help you put the science into context.

[1] Forensic Science Regulator: DNA Mixture Interpretation (FSR-G-222).


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