DNA transfer - a vital issue in many trials

We have produced a number of articles commenting on the vexed matter of using DNA profiles to infer the mode of transfer to the surface on which it is found (e.g. Comment on DNA transfer, Article in New Scientist).

Dr Meakin (who was a scientist at The Forensic Institute at the time of writing the paper) and Professor Allan Jamieson have published a peer-reviewed assessment of the published literature to date on the transfer of DNA which is becoming a major issue in many criminal trials.

" This review presents and considers data from trace DNA experiments to establish whether the quantity of DNA recovered from a crime stain and/or the quality of a DNA profile obtained can be used to infer the likely mechanism of transfer. The data show that varied results are obtained from apparently similar trace DNA samples, presumably due to the many factors that affect the detection of trace DNA.  The nature and effect of these varying factors and the application of the data to casework is considered generally and with specific reference to DNA transfer to skin, DNA beneath fingernails, ‘wearer DNA’, and various contamination considerations."

Sequential unmasking: minimising observer effects in DNA interpretation

This is a letter signed by eleven international experts, including Professor Allan Jamieson, recommending a 'blind' approach to DNA interpretation which prevents the analyst being unduly biased by knowing the profile of the suspect before they interpret the DNA profile.

DNA statistics

A series of recent Appeal Court judgements has seen the triumph of scientific experience over experiment, and the relegation of DNA evidence from the gold standard of scientific evidence to no more than a subjective opinion.  The recent case at the Court of Criminal Appeal for England and Wales of Dlugosz represents the final stage in the descent of DNA evidence, and perhaps scientific evidence generally, to subjective guesses based on the somewhat awkward, limited, and difficult to assess concept of the experience of the scientist (if that professional name can be applied in the circumstances). This Barrister magazine article presents and discusses the series of Appeal Court decisions that leads us to this view.

The verbal scale

"Our aim was to assess the extent to which the verbal expressions used by the expert in court are perceived and the extent to which they are differentiated by potential jurors. Four hundred volunteers were asked to indicate the level of strength they perceived from the use of the verbal scale characters within excerpts from purported expert witness statements. Although preliminary, these results show that there are serious misunderstandings of the verbal scale. It does not achieve the purpose for which it was created. The terms used are unlikely to be understood properly by lay people and it would appear that they are actually misunderstood."

This paper, a collaboration with University of Glasgow, was published in December 2013.

Low copy number (LCN) or Low Template DNA (LTDNA)

"Low Copy Number DNA (LCN) analysis has acquired a high profile in forensic circles, but has gained more attention following judicial criticism of the technique’s reliability in the Omagh Bomb trial, R v Hoey. The judgement was quickly followed by a review conducted on behalf of the new Forensic Regulator (Caddy Review), which gave the technique an apparent clean bill of health. However, the conclusions set out in the review have attracted criticism and have not led to agreement about the general use of LCN analyses. The judgment in Reed & Reed deals with two issues. The first is the admissibility of evidence of this type of analysis. The second, and perhaps more contentious issue, concerns whether an expert witness ought to be permitted to provide an opinion as to the likelihood and means by which DNA might have been transferred to the place where it was discovered. ...

The judgment in Reed and Reed should not be viewed as having foreclosed the possibility of challenges to the admissibility of LCN DNA analysis in future cases. These clearly should be possible in what amount to the same conditions as they were challenged before, the presence of variable results. Almost all LCN cases start with amounts of DNA typically less than 100 picograms.  As to the criminal justice system’s faith in experience as evidence of scientific expertise, whilst experience in science is useful, it augments but does not replace the foundations of scientific knowledge. This decision, and similar recent decisions, have undoubtedly stirred the wider scientific community to react to what it sees as an attack on what gives science its enviable reputation (and value in court): published, validated, peer-reviewed, experimentally controlled research as the basis for operating procedures and interpretational rules for practical applications."

This article expands the arguments.

Following the Appeal Court ruling in Reed & Reed in December 2009, Professor Allan Jamieson considers the potential implications for other Low Copy Number (LCN) DNA cases involving the use of DNA profiles below the stochastic threshold.

Scientific and professional standards

Articles and an editorial in one of the world's premier scientific journals, Nature, continue recent criticism of the need for better science in forensic science. In particular, one of the Nature articles focussed criticism on the technique of Low Copy Number (LCN) DNA. A technique designed to analyse amounts of DNA below that for which the standard kit was designed, and which has attracted adverse comment across the world.

In response to this criticism, Professor Allan Jamieson of The Forensic Institute had a letter published in Nature suggesting that the UK approach was unlikely to solve the problems of standards in forensic science and recommending a new review of the use of LCN methods.

"I look forward to the development of a satisfactory model in the United Kingdom.  In the short term, a fresh, deeper and wider look at the use of low-template DNA  techniques, particularly in casework, is overdue."

 The NAS Report and the Law Commission Consultation Paper on Forensic Science

Recent publications from the National Academy of Science (USA) and the Law Commission (UK) provide an interesting contrast in approach to well documented and historic problems with the use of “scientific" evidence in legal proceedings. The NAS recommends a thorough assessment of the scientific bases of forensic science, to discern and improve the validity of the science before it can be considered suitable for court purposes. The UK approach more tentatively examines the legal admissibility of forensic science, leaving aside the more fundamental questions as to the inherent unreliability of the evidence. Drawing upon the American report and current experience in the UK, this paper proposes a more robust admissibility regime in the UK, including recognition and acceptance of the different roles of the prosecution and defence expert; more thorough and less combative disclosure by the prosecution; wider availability of validation data; and greater legal and research support for the thorough review of the “science" underlying forensic science.

This article was written by Dr Rhonda Wheate (formerly at TFI), and Professor Allan Jamieson

The Philosophy of Forensic Identification

This Article discusses some of the features that make a process scientific, outlines the forensic process through which evidence must travel, considers the principles and practice of individualization, and finally describe the difficulties of assessing the significance of any “match”, with particular emphasis on DNA profiling. 

Report on Fire Investigation in Scotland

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