This judgement of the Appeal Court in the jurisdiction of England and Wales was delivered in 2010 and produced what may well have been the greatest response yet from the forensic science community, both academic and practitioner. The assumed support of practitioners is based on the support of ENFSI (European Network of Forensic Science Institutes) directors; i.e. directors of state forensic science laboratories throughout the Europol region.
While the judgement is in fact limited to foot wear marks it is not entirely clear on the point and legal commentators have extended the scope to include other evidence types.
What prompts this statement is that, as feared, R v T is being used to argue that any evaluation using a logical framework, i.e. based on a likelihood ratio approach, should not be admitted. When it suits their purpose, advocates are looking to the judgment as a means of excluding expert opinion evidence based on a likelihood ratio approach.
The purpose of this statement is to clarify the position of Linked Forensic Consultants. We are of course not qualified to comment on the legal aspects of the judgement; our comments are limited solely to the science.
The position of Linked Forensic Consultants regarding the scientific basis of the judgement is as follows.
- The judgment was right in its criticism of the use of unreliable data and a lack of transparency.
- The judgement was helpful in highlighting the need for expert evidence to be closely scrutinised prior to admission.
- The judgement was erroneous in rejecting a logical framework for the evaluation of expert evidence.
- The judgment was unhelpful in suggesting an opinion such as ‘could have’ would be helpful to the trier of fact.
The response of Linked Forensic Consultants to the judgement is as follows.
- There are circumstances in which the use of a logical framework for the evaluation of forensic evidence is inappropriate, but these are few.
- The likelihood ratio stands apart from Bayes’ law and using the terms ‘Bayes’ and ‘Bayesian’ in connection with the likelihood ratio approach can be misleading and is confusing (Bayes’ law may be stated as Posterior is proportional to LR x Prior; posteriors and priors are of no concern to the expert witness).
- We agree with Berger that the likelihood ratio approach is ‘logical and it is coherent. Furthermore, it is the only logical and coherent approach to forensic science interpretation. There are no others’. See Berger et al, Science and Justice 51 (2011) 215.
It is fair to say that from the perspective of forensic science this judgement seems confused. Other judgments which seem to take a variety of positions on a logical framework and evaluative evidence are;
- R v Doheny and Adams [1996] EWCA Crim 726,
- R v George [2007] EWCA Crim 2722, and
- R v Reed, Reed and Garmson [2009] EWCA Crim 2698.
Other relevant papers are
Evett I.W. et al (2011) Science & Justice 52, 1–2.
Redmayne M. et al (2011) Crim.L.R #5
In passing, we are astonished at the implication of not criticising the expert witness. Surely an expert must be responsible for his or her own competence? Excusing the expert on the grounds that he was following the standard practice within the Forensic Science Service (FSS) at the time seems extraordinary and the court’s silence on any remedial action equally extraordinary.
Sean Doyle
29/4/13
©2013 Linked Forensic Consultants Ltd. All rights reserved.
A recent story on a New Zealand news website highlights the poor accuracy of press reporting, if any further evidence were needed. It also draws attention to a report by a lawyer and psychologist which makes a number of familiar recommendations regarding expert evidence.
The headline bears little relation to the contents of Henderson & Seymour's report which is the basis of the story. The headline is drawn from one paragraph in 167 pages and casts an unjust slur on experts called by the defence. The headline suggests an agenda.
The report concerns experts who testify in both the criminal and Family Courts in New Zealand regarding child abuse and neglect, highly controversial and emotive areas of forensic practice far removed from the 'gold' standard of DNA profiling.
Child abuse cases are prone to experts using the witness box to promote their own theories as demonstrated by the case of the paediatrician Professor Sir Roy Meadow. Professor Meadow gave evidence for the Crown in a number of trials of mothers charged with killing their infant children. He relied on flawed statistical analysis and flawed science; a theory he invented [see Meadow R. 1977. "Munchausen syndrome by proxy (MSbP). The hinterland of child abuse" Lancet 2 (8033): 343–5.] is considered by many medical practitioners to be without scientific foundation. Australia and the UK have established the legal precedent that MSbP does not exist as a medico-legal entity. Indeed, the scientific foundation of expert opinion offered in child abuse cases appears to be a common issue as evidenced by a quote from R v Henderson [2010] EWCA Crim 1269.
“Can the witness point to a recognised, peer-reviewed, source for the opinion? Is the clinical experience of the witness up-to-date and equal to the experience of others whose evidence he seeks to contradict?”
The report of Henderson and Seymour is based on 'qualitative empirical research'; gleaning the opinions of expert witnesses and validating those opinions by reference to lawyers. It is a useful and scholarly review particularly if the areas of forensic practice covered are of interest. However, it contains little that is new, omits some important areas of scholarship on the evaluation of scientific evidence and bias, recycles prosecutorial ‘myths’ (defence disclosure delays) and its recommendations have a familiar ring.
As I have written elsewhere (e.g. Dominion Post, Letters, 26/12/12), justice is best served when the expert evidence is relevant and expert witnesses are objective, impartial, competent, possess practical experience in their specialism and understand their role. Unfortunately that is not always the case. The remedy lies with the experts.
Other issues such as the often gross inequality of arms between the defendant and the State are matters for all the stakeholders.
Sean Doyle
26th of March 2013
Copyright 2013 Linked Forensic Consultants Ltd
