Forensic science and the criminal justice system: a blueprint for change Contents

Chapter 5: The use of forensic science in the criminal justice system

Discrepancies between prosecution and defence provision

Legal aid

117.Legal aid rates have led to difficulties for defendants in criminal cases commissioning forensic tests and experts. The Legal Aid Agency requires three quotes for forensic experts to be obtained and the reasons why forensic testing is necessary. It will then decide if testing is justified and will normally authorise the cheapest of the three quotes obtained.

118.Dr David Schudel told us that the presumption in favour of the cheapest quote by the Legal Aid Agency “is regardless of quality and whether it is even fit for purpose … More fundamentally, for a lot of the work we do, such as DNA, fingerprints and the digital arena, the legal aid rate now is less than it was in 1999. So, we are really struggling.”137 Dr Anya Hunt, the Chief Executive Officer of the Chartered Society of Forensic Sciences, thought this lack of focus on quality sent a poor message about the need for trustworthy and accredited practitioners to be providing forensic expertise.138

119.The requirement to justify why forensic science evidence needs to be challenged requires some expertise by the lawyer, as explained by Professor Carole McCartney, from the School of Law at Northumbria University:

“You might just know that there is DNA involved in the case, but in order to interrogate that and get beyond simply “There is a DNA match in this case” you need to understand what that means, what its significance is and whether you need to consult an expert. However, if you cannot demonstrate to the Legal Aid Agency that there is something challengeable there that needs to be investigated, then there is a chicken-and-egg situation: you have to have some expertise to be able to demonstrate that you need legal aid to go and get yourself a defence expert.”139

120.Chris Henley QC, Chair of the Criminal Bar Association, told us of an experience in which a defendant “could not get the funding for a DNA expert from the Legal Aid Agency, so in the end, on a prayer, she called the author of a textbook, who agreed to do it for nothing.”140 Dr Karl Harrison added that he had “been commissioned by the police, by prosecuting authorities something like 160 times in my career and I have been commissioned by defence counsel three times. This reflects the level of funding that is available to challenge specialist forensic evidence.”141

121.Paul Harris, Senior Partner at Edward Fail, Bradshaw & Waterson Solicitors, explained that these issues with legal aid had created a discrepancy not just between the defence and prosecution, but between privately funded and legally aided client.142

122.Lucy Frazer QC MP said that “legal aid should be available, as with any disbursement, if there is a sufficient benefit to the client in the case in the instruction of a forensic expert report and the cost of the expert is reasonable. Thus legal aid should be available for the forensic expert.”143 It is clear that these rules are not always being applied fairly or consistently.

123.Cuts to legal aid have affected the ability of defendants to access forensic expertise. We recommend that the Legal Aid Agency liaise with the market-regulation arm within the expanded role of the Forensic Science Regulator to set new pricing schemes, properly funded by the Ministry of Justice, for forensic testing and expert advice for defendants.

Understanding of forensic science in the criminal justice system

124.We have considered how forensic science is used in criminal cases and how science evidence is understood and interpreted by legal professionals. There is a wide variety of forensic science evidence that can be admitted as evidence in criminal cases. Depending on the case, there can be different requirements for science evidence ranging from attributing the ‘source’ of forensic material (e.g. the identity of a person from a DNA profile) to reaching conclusions about the activities that led to the generation and/or transfer of material (e.g. how and when the DNA was transferred and the relevance of its presence in a particular location or on a specific item). There is a need for consistent interpretation by judges and lawyers of what the evidence means in a specific case to ensure the fair and consistent application of the law.

Lawyers and judges

125.Our evidence showed a mixed level of understanding of scientific issues by lawyers and judges. Sarah Whitehouse QC, a Barrister at 6KBW, told us that “the general levels of understanding among the judiciary and the Bar are very good, because they are adept at absorbing new scientific ideas and concepts quite quickly.”144 However, Dr Gillian Tully said that “the understanding of forensic science amongst lawyers and judges appears, from transcripts and judgments, to be variable. Judgments have on occasion demonstrated a lack of understanding of the process of scientific reasoning”.145 Forensic science is constantly developing; this can lead to difficulties for legal professionals in understanding the complex forensic science evidence presented, and its limitations.

126.Problems can arise due a lack of familiarity with a specific type of evidence. Angus Marshall, Director and Principal Scientist at n-gate Ltd, told the committee of an experience presenting digital forensic evidence to legal professionals:

“I find that prosecutors, in particular, do not seem to have time to properly read my reports, or to consult with me in order to fully understand the evidence I have presented. Indeed, it has been the case that during the presentation of evidence … , I have had to disagree with and correct a member of counsel who has completely misunderstood my evidence because his understanding of the technical issues was based on incorrect assumptions and personal experience of a completely different, but superficially similar, system.”146

127.Difficulties can also be caused by the inherent scientific complexity that exists when dealing with uncertainty. UCL Centre for the Forensic Sciences highlighted a recent study of 108 laboratories across the USA in which the laboratories were asked to interpret a series of mixed DNA profiles.147 “For one of the complex mixtures in that study, 78 laboratories (69%) incorrectly included a donor who was not present in the mixed profile. Seven laboratories correctly excluded this donor (6%), but the reasons for the correct exclusion varied.”148 The evidence presented to the court will not always make it clear how a DNA match was obtained from a complex mixture. Advocates need to have the knowledge to bring these differences out during their examination of witnesses.

128.An incorrect understanding of probability by legal professionals can lead to evidence being given more weight that it deserves. Professor Norman Fenton from the Alan Turing Institute explained the dangers of evidence being wrongly interpreted in the courtroom:

“While some common errors of probabilistic reasoning are well known and even recognised as dangerous by the judiciary (such as the prosecutor’s fallacy149), most are not. I believe injustices are occurring widely because of misunderstandings about the probative value of forensic match evidence. Specifically: what can we reasonably infer if there is evidence that some forensic ‘trace’ (which could be DNA, a fingerprint, a shoe mark, a fibre, etc) has a profile that matches the profile belonging to a particular person? It is widely (but wrongly) assumed that if the ‘trace’ is DNA or a fingerprint than the profile match is equivalent to an identification, i.e. that the trace must have come from the person. However, because many forensic traces from crime scenes are only ‘partial’ and may be subject to various types of contamination, the resulting ‘profile’ is not sufficient to ‘identify’ the person; many people would have a partial profile that matches.”150

129.A further difficulty is the challenge of providing clear evaluative interpretations of what the evidence means to a court. A number of witnesses highlighted the gaps that exist in being able to deliver evidence-based interpretations of forensic science evidence.151 For instance, without better empirical data about transfer and persistence of DNA, interpretations of results by experts in court must remain subjective.

130.There is statutory guidance for lawyers and judges regarding expert witnesses set out in the Criminal Procedure Rules152 and the Criminal Practice Direction153 which must be read together; the reason for two documents is historical and technical; they have been drafted together and approved by the same body. They set out the following requirements if expert evidence is to be admitted in a trial:

131.In 2017 the Royal Society and the Royal Society of Edinburgh produced, in conjunction with the judiciary in England and Wales and Scotland, the first two in a proposed series of primers written by leading scientists and judges to assist judges in handling forensic scientific evidence by providing an easily understood and accurate position on different types of forensic science evidence. The two primers provide overviews of forensic DNA analysis155 and forensic gait analysis.156 Primers on further topics are planned. While the reception to these has been positive, the initiative has received no Government support. While the project has demonstrated the utility and importance of what it set out to do, it needs proper financial support if it is to provide broad coverage within a sufficiently rapid timescale for the project to be the source of ongoing, balanced and accessible advice on forensic science evidence put before the courts.

132.The Inns of Court College of Advocacy, in conjunction with the Royal Statistical Society, has produced a guide for barristers on statistics and probability, and how to understand statistical evidence in court.157 The Inns of Court College of Advocacy has also produced a guide to the preparation, admission and examination of expert evidence.158 These are potentially useful resources but it is not clear how widely used they are by legal practitioners.

133.Aside from criminal practice directions and primers, there are few other resources for judges and lawyers, and no formalised training in forensic science. Dr Christopher Lawless, Associate Professor at Durham University, suggested this could be rectified by incorporating elements of scientific method into undergraduate law programmes.159

134.Professor David Ormerod QC, Chair in Criminal Law at UCL and Law Commissioner for England and Wales, suggested

“that there is scope for a compulsory element to the newly qualified practitioners scheme. Everyone who qualifies as a barrister or solicitor has to undertake continuing professional development … There is an opportunity there for a compulsory module relating to forensic science.”160

Similar training could be provided for judges161 through the Judicial College.

135.The new Forensic Science Board should have ultimate responsibility for ensuring ongoing guidance to the judiciary and the legal professional about the accurate scientific position on the main types of forensic science. Although this must be a matter for the Board, there is clear benefit in continuing the work that has produced primers on key topics, albeit at an increased pace and with a broader scope. They should be responsible for enabling dialogue and sharing of best practice, and responding to new developments as they arise.

136.We recommend that all advocates practising in the criminal courts should, as part of their continuing professional development, be required to undertake training in the use of scientific evidence in court and basic scientific principles such as probability, scientific inference and research methods.

The ‘CSI effect’

137.There is concern about how juries treat forensic evidence. The Scottish Police Authority described the ‘CSI effect’ in juries as “primarily shaped by the media and television” and “not based in anyway in reality”.162

138.Sarah Whitehouse QC told us that “juries do not always understand that forensic science is not a magical golden key and that they must slot the scientific evidence they hear into the context of the other evidence in the case. Too often they … think that DNA will solve everything.”163 This was supported by His Honour Judge Wall QC, a Circuit Judge, who told us the ‘CSI effect’ “has led to juries constantly asking questions in a trial as to whether something has been submitted for testing, and if not, why not. It also leads … to them having a great deal of confidence in the scientific evidence and … putting more emphasis on its importance than it really has in any trial.”164

139.There is limited published evidence on how the portrayal of forensic science in the media affects juries’ perceptions of forensic science. However, the anecdotal evidence that we heard suggests that it is an issue that needs to be considered.

140.Further research is necessary. One suggestion for counteracting the ‘CSI effect’, put to us by Dr Itiel Dror, Senior Cognitive Neuroscience Researcher at UCL, was for the jury to be shown a video where there was “DNA evidence, fingerprint evidence, giving the reality and the strengths of the forensic domain”.165

Streamlined Forensic Reporting

141.We heard evidence which raised concerns about the use of Streamlined Forensic Reporting (SFR) in court which were first introduced in 2012. The purpose was, according to the Crown Prosecution Service that SFR “seeks to reduce unnecessary costs, bureaucracy and delays in the criminal justice system. The process takes a more proportionate approach to forensic evidence through the early preparation of a short report that details the key forensic evidence the prosecution intend to rely upon.” This is aimed at achieving “early agreement with the defence on forensic issues but where this cannot be achieved in the first instance, to identify the contested issues.”166

142.Sarah Whitehouse QC thought that SFR could “save a great deal of time and money and … allow early engagement by the defence in obtaining their own forensic experts”.”167

143.It is clear that problems arose in relation to the use of SFRs. The main issue seemed to be that the initial SFR report (SFR1) was being used at trial instead of the more comprehensive SFR2. As a result, the Senior Presiding Judge of England and Wales issued firm guidance in March 2017 which explained that SFR1 “involves the provision of a short report, written by the relevant provider, which gives the initial key findings. This is not a witness statement nor an expert’s report, which would require the level of detail specified in CrimPR r19.3(3).”168 It was therefore not admissible evidence at a trial. The guidance explained that the SFR was to be used only to see if the prosecution case on the forensic investigation as set in the SFR1 was agreed by the defence; if it was not, then the SFR1 was not to be used in court, but a SRF2 or a full report should be used. The guidance explained that in contrast, “SFR2 evidence is prepared by the relevant person or expert, and it is presented in witness statement format with an expert’s declaration under CrimPR 19.4(j) and the 2015 Criminal Practice Directions 19B, if required.”169 The guidance should have resolved the issues, but we heard some evidence that it had not.170

144.Adrian Foster, Chief Crown Prosecutor at the Crown Prosecution Service, accepted that this was a problem in some cases and that “some prosecutors, judges and defence counsel are asking for the witness who created the SFR1 to come to court. That is the wrong person. They are just the author of the findings. You need the expert who actually carried out the work and that is the person who should write the SFR2.”171

Digital evidence

145.Digital evidence is now a key component in many criminal trials. Mark Stokes estimated that “90% of crime … has a digital element, in the broadest sense of that: CCTV, communications data, social media data, cyberattacks.”172 Witnesses told us about the amount of data that is prevalent in most investigations and the difficulties of interrogating the evidence in an acceptable timeframe. Angus Marshall explained that “the privacy issues and the increase in security that has been put on to devices … presents challenges to us.” This was coupled with most devices having large storage limits so “there is a limit to how quickly we can extract data from devices, so that adds time in every investigation.”173

146.Digital forensic practitioners told us that lawyers often do not understand the practicalities of analysing digital evidence and the amount of time and manpower involved. Dr Jan Collie, Managing Director and Senior Forensic Investigator at Discovery Forensics, said that defence lawyers “frequently do not think about the potential value that the digital evidence might have in a particular case. Therefore, they are racing to the finish and they think about it a couple of weeks before the trial … There is quite a lot of disorganisation there.”174

147.Professor Peter Sommer told us that this disorganisation was often displayed by judges as well: “judges must have much better case management where there is digital evidence.”175 In particular, they should have a better sense of the capabilities of the forensic scientists working on the case. Mark Stokes explained that the digital forensic unit in the Metropolitan Police had “a seven-month backlog.” They were working to reduce that backlog through outsourcing but he was clear that they “cannot meet the demand currently with what we have.”176 The evidence was clear that very considerable investment was needed in the use of modern technology to search and analyse digital content.

148.Digital forensic evidence also has specific issues with commercial confidentiality when it comes to revealing how data were extracted and analysed. Sir Brian Leveson told us about a case in which:

“the contents of a phone had been wiped … and there were great difficulties finding out what had been on the phone. However, a commercial provider managed to download or retrieve some of the messages. The defence wanted to know how they had done that and the scientist was not prepared to explain it, first, because it was commercially confidential and, secondly, if he explained how he had done it, the next time round they would find a way of avoiding that problem.”177

149.Digital evidence will become even more prevalent in trials in the coming years. There needs to be a better understanding among legal practitioners of the timescales involved in interrogating and analysing digital evidence where modern technology is not used; this must be built into the pre-trial process.

150.The Ministry of Justice and the Home Office should invest in research of automation techniques for data retrieval and analysis to reduce the resources and time taken to process and analyse digital evidence and thus reduce delays in the criminal justice system. In doing so, they should assess the use of these techniques in the civil court system and consider what other examples of best practice could be replicated.

151.We recommend that the Government works urgently to build capacity and resilience in digital forensics. The new role of the Forensic Science Regulator should take into account the need for digital forensic capacity in the course of regulating the market.

137 Q 117 (Dr David Schudel). Dr Schudel represented Keith Borer Consultants whose work is mostly for the defence.

138 Q 117 (Dr Anya Hunt)

139 Q 57 (Professor Carole McCartney)

140 38 (Chris Henley QC)

141 Q 7 (Dr Karl Harrison)

142 Q 134 (Paul Harris)

143 Q 231 (Lucy Frazer QC MP)

144 Q 133 (Sarah Whitehouse QC)

145 Written evidence from Dr Gillian Tully (FRS0057)

146 Written evidence from Mr Angus Marshall (FRS0019)

147 JM Butler, M.C. Kline, M.D. Coble, ‘NIST interlaboratory studies involving DNA mixtures (MIX05 and MIX13): Variation observed and lessons learned’, Forensic Science International: Genetics, Volume 37 (November 2018), pp 81–94:–4973(18)30248-5/fulltext [accessed 27 March 2019]

148 Written evidence from UCL Centre for the Forensic Sciences (CFS) (FRS0041)

149 Norman Fenton and Martin Neil, ‘Avoiding Legal Fallacies in Practice using Bayesian Networks’, Australian Journal of Legal Philosophy 36, 114–151 (29 June 2011): [accessed 27 March 2019]

150 Written evidence from Alan Turing Institute (FRS0030)

151 See written evidence from NCECJS (FRS0038), UCL Centre for the Forensic Sciences (CFS) (FRS0041), James Hutton Institute (FRS0042), Lancashire Forensic Science Academy (FRS0054), and Dr Gillian Tully (FRS0057).

152 The Criminal Procedure Rules—October 2015 as amended April 2018, Part 19, Expert Evidence: [accessed 4 March 2019]

153 Criminal Practice Directions—October 2015 as amended November 2016, April 2017, October 2017, April 2018 and October 2018, Criminal Practice Directions 2015 Division V: [accessed 4 March 2019]

154 The Practice Direction sets out the factors enumerated by the Law Commission in its 2011 Report. Consideration of the factors should ensure a thorough examination of the underlying scientific reliability of the evidence.

155 The Royal Society, Forensic DNA analysis: a primer for courts (November 2017): [accessed 14 February 2019]

156 The Royal Society, Forensic gait analysis: a primer for courts (November 2017): [accessed 14 February 2019]

157 The Inns of Court College of Advocacy (ICCA), Royal Statistical Society (RSS), Statistics and probability for advocates: Understanding the use of statistical evidence in courts and tribunals (2017): [accessed 15 February 2019]

158 ICCA, Guidance on the preparation, admission and examination of expert evidence (2019): [accessed 19th February 2019]

159 Q 23 (Dr Christopher Lawless)

160 Q 56 (Professor David Ormerod QC)

161 Written evidence from Professor Wolfram Meier-Augenstein (FRS0032)

162 Written evidence from Scottish Police Authority (FRS0084)

163 133 (Sarah Whitehouse QC)

164 Q 177 (His Honour Judge Wall QC)

165 Q 28 (Dr Itiel Dror)

166 CPS, Streamlined Forensic Reporting Guidance and Toolkit (2017): [accessed 14 February 2019]

167 Q 140 (Sarah Whitehouse QC)

168 Judiciary of England and Wales, Better Case Management (BCM) Newsletter, Streamlined Forensic Reporting, Issue 12, March 2017, p 2: [accessed 26 February 2019]

169 Judiciary of England and Wales, ‘Streamlined Forensic Reporting’, Better Case Management (BCM) Newsletter, Issue 12, p 3

170 Q 111 (Dr David Schudel)

171 37 (Adrian Foster)

172 Q 126 (Mark Stokes)

173 121 (Angus Marshall)

174 Q 126 (Dr Jan Collie)

175 Q 125 (Professor Peter Sommer)

176 Q 131 (Mark Stokes)

177 Q 178 (Sir Brian Leveson)

© Parliamentary copyright 2019