Jo Millington wrote an article for the Winter Issue of the Expert Witness Journal (April 2019, pp34-36).
In 1953, Paul Kirk (1) wrote ‘All criminal investigation is concerned either with people or with things. Only people commit crimes but they invariably do so through the medium of things. It is these things that constitute the broad field of physical evidence. To realise his maximum goal the investigator must understand a) what physical evidence is b) how to collect and preserve it and c) how to obtain from it the information that it carries and d) how to interpret the information obtained. Only a good understanding of investigators and scientists of their reciprocal functions can completely eliminate the barrier to the realization of the full benefits of a well-managed crime laboratory’.
Kirk then outlined how this could be achieved through the regulation, validation and accreditation of forensic science and demonstrated how each aspect is dependent on collaboration. Collaboration, communication and corroboration are pillars of forensic science, as well as lots of other things, another being impartiality. A robust and holistic strategy (big S) is therefore critical in driving forensic science in the right direction.
Those who have worked in, or with, the forensic science industry in the UK will know that forensic science policy has evolved consistently over the years. This was most recently bookmarked with the publication of the government’s Strategy on Forensic Science (2). Read in conjunction with the UK Forensic Science Regulator’s Codes of Practice and Conduct (3), both strive to bring coherency to a challenged forensic science framework. The proposed strategy states that ‘a national approach to forensic science delivery, proposed and delivered by police forces, would aim to ensure greater consistency of service quality; resilient, reliable capability and with economies of scale’. Proposed and delivered by police forces.
At the time of writing the House of Lords Science and Technology Committee inquiry into Forensic Science (4) had attracted 96 written submissions from representatives across the Criminal Justice System (CJS) and had convened 16 sessions of oral evidence. The evidence is compelling and I would encourage all stakeholders in forensic science to read the transcripts. The inquiry has facilitated one of the most comprehensive and refreshingly open discussions on forensic science in recent times. The clarity and candour of the submissions are less sugar-coated than those made to the previous Select Committee, convened in the aftermath of the closure of the Forensic Science Service. It has included discussions on standards and regulation, the forensic science research landscape, use of forensic science in the CJS, and digital forensics. It is crystallising the view on where the shortfalls lie: lack of investment, a fragmented approach to forensic investigation and building concern that the overarching ‘strategy’ behind it’s future development has been police-led with little or no discernible contribution from forensic science providers, or forensic scientists.
The national strategy also suggests that it is relevant to forensic science, full stop, and yet it is weighted towards biometrics, fingerprints and digital investigations. You could argue that this simply reflects evidence in today’s crimes – I doubt you go anywhere without your mobile phone as much as you would be reluctant to leave your fingerprint behind, especially if you were up to no good. These areas are traditionally delivered ‘in-house’ by police forces and so perhaps it is inevitable that the strategy board would focus on their own strengths. The question is, are they doing so at the detriment of everything else?
Stuart Kind’s book ‘Science Against Crime’ (5), which was published nearly 30 years on from Kirk, takes the reader on a similar journey through the evidence types that were typically dealt with in a forensic laboratory of the time. There is no entry for digital or cyber crime, no mobile phone tracking or social media profiling, but both authors talk extensively about the work of the forensic science laboratory and the potential of blood, toxicology, ballistics, glass and fibres in crime investigation.
If you search the Forensic Science Strategy document, each of these evidence types (blood, ballistics, toxicology, glass, fibres) generates 1 match, each. The term fibre highlighting that the document would be printed on paper containing 75% recycled fibre content. There are 70 matches to the word digital, 33 to DNA, 14 to fingerprints.
If the aim is to define a national and cohesive strategy on forensic science it is imperative that all disciplines are considered and all parties are consulted, unless you can guarantee that the people involved have sufficient oversight and knowledge of the strengths and weaknesses of the whole process in order to be able to represent every part of it fairly. If it is intended that the strategy will simply sit alongside the forensic science laboratory, with investigators directing scientists to conduct tests on a case by case basis without inviting them to advise in the selection of those tests, in my view the relationship between the scientist and the investigator will inevitably degrade. Especially when there is increasing pressure to deliver results more quickly and for less money. Cost-efficiencies are not simply a function of picking the cheapest option. They can be achieved by using the right test for the job. If tests are selected on the basis of price but they do not have the ability to answer the question that is being asked, then it can introduce inefficiencies further down the line. This can include commissioning additional tests as the case approaches trial, which in itself can introduce risk.
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. So does it?
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 that indicates if each of the profiles had been generated using the same DNA technology, or if the crime profile may have comprised a mixture of DNA, although this level of detail might not be readily apparent to the non-scientific reader. Having reviewed a number of police interviews, it is not unreasonable to 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. While your brain is working on recalling your pin number, perhaps you could also 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, which unfortunately is not something you can opt out of. In my opinion, 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.
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 in 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 in hospitable of samples.
If, or inevitably when, the resulting profile comprises a mixture of DNA, it might be 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 DNA information 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 supported6 (or necessary) given the intro duction 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.
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. It is not unusual for reports of this type to focus on the make-up of the DNA result and any possible matches. They may include phrases to emphasise that they do not deal with a full interpretation of the findings and if this was required 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’. Although and there are a number of research publications emerging on this topic, the data set is by no means complete.
It’s not acceptable (is it?) that the meaning of the scientific findings, a DNA result for example, could change significantly depending on when the evidence is introduced into the CJS. Whether it has been fully evaluated in context with the case circumstances (or not) or because the results have been conveyed in a particular type of report. 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 my advice would be 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 con sidered as undefined.
The Forensic Science Regulator has published a number of comprehensive documents on how forensic science should be delivered and communicated. The Codes of Practice and Conduct are a modern day equivalent of Kirk and Kind and I would encourage any users of forensic science to read the guides that are relevant to their area of expertise. It is clear that regulation and accreditation have a pivotal role in the delivery of a consistent service, but the Lords’ inquiry has highlighted the difficulties that many organisations are experiencing. The (often prohibitive) costs associated with applying for and reaching accreditation are a recurrent concern, even though there is a genuine appetite to achieve accreditation. On-going resource requirements to demonstrate and maintain standards should not be underestimated. These challenges apply as much to police forces as they do to the sole trader or larger forensic science providers, most notably in the accreditation of fingerprint examinations and digital forensics. Yet these disciplines are central to the Forensic Science Strategy in the UK, which police forces and their affiliated agencies are driving. It is becoming increasingly difficult for stakeholders to comply with the rules that they are setting and it begs the question, wouldn’t it be easier if we all worked together and pooled our resources?
In order to deliver a rational and coherent national forensic science strategy the industry urgently needs investment. We also need to take a cooperative approach to education and communication so that all users understand the strengths and limitations of the evidence, in the form that they are likely to encounter it, at each stage of an investigation. My fear is that the current strategy will stifle forensic science in the UK. We need to build on the strong foundations of the past and nurture a multi-faceted service that has the ability to deliver scientific findings consistently and dependably in the future. We need, joined-up thinking.
1, Kirk, P. Crime Investigation: Physical Evidence and the Police Laboratory. 1953. Interscience, New York.
2, Forensic Science Strategy: A National Approach to Forensic Science Delivery in the Criminal Justice System. March 2016.
3, Forensic Science Regulator: Codes of Practice and Conduct. October 2017. Issue 4.
4, House of Lords inquiry: Forensic Science. 2018-2019. https://www.parliament.uk/forensic-science-lords-inquiry (accessed January 2019).
5, Kind, S. 1982. Science Against Crime. Marshall Cavendish Books Ltd, London.
6, Forensic Science Regulator: DNA Mixture Interpretation (FSR-G-222).
Jo Millington BSc (Hons) MSc PGCert MIABPA MCSFS
Occupation: Forensic Scientist / Director Millington Hingley Ltd: Forensic Scientists
Contact details: firstname.lastname@example.org