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What DNA can and can't tell us in criminal investigations must be clear

January 24, 2017

DNA analysis has revolutionised forensic science; helping to catch prolific murderers and exonerating innocent people wrongfully convicted of serious crimes. But as DNA profiling has become increasingly sensitive and is used in more investigations, it is essential that public and professional expectations of this technology come not from TV crime fiction, but from reality.

To address existing misconceptions and share exciting new developments, researchers from the European Forensic Genetics Network of Excellence (EUROFORGEN) are launching a guide in partnership with the charity Sense about Science. Making Sense of Forensic Genetics shares what DNA analysis can currently do in the criminal justice system, what its limitations are, and what might be possible in future. It includes case studies, both where DNA evidence has been a game changer in investigations and where its misinterpretation has led to miscarriages of justice.

The researchers share their insights:
  • Despite claims to the contrary, predicting visible traits such as face shape from DNA is not currently possible. There are reports of police departments using tests that claim to predict face shape, but these tests are not scientifically validated. The latest advances in forensic genetics are beginning to enable some externally visible characteristics including hair and eye colour to be predicted from someone's DNA. This could be a powerful investigative tool in future. But there are limits to what we can currently tell from DNA.

  • Your DNA could be in a room even if you weren't. Our DNA is everywhere - it can be transferred by saliva from talking, sneezing, coughing and by shedding skin cells. There is even DNA present in house dust. So DNA from individuals who have nothing to do with a crime might be present at a crime scene.

  • DNA alone doesn't solve crimes. Advancements in forensic DNA techniques mean that we can now detect minute traces of DNA. The presence of DNA doesn't establish guilt - and doesn't necessarily tell us when or how it got there or the body tissue it came from (particularly for very small amounts). Therefore, context has become increasingly key, and now more than ever, DNA needs to be viewed within a framework of other evidence. It's an important detection tool, but it's certainly not a detective.

The report makes reference to landmark cases including cases where DNA has been a game changer; helping to catch prolific serial killer Gary Ridgway (page 15), and where it has caused miscarriages of justice; Adam Scott being detained and charged with rape due to a contamination error whilst subsequent phone records placed him in a different city at the time of the crime (page 7).

For more information about the guide and partnership with EUROFORGEN, contact: Emily Jesper at Sense about Science +4420 7490 9590 / out of hours: +447863 140387


Manfred Kayser, Professor of Forensic Molecular Biology, Erasmus MC University Medical Centre, Rotterdam and EUROFORGEN researcher: "Currently eye colour, hair colour and skin colour can be predicted reliably and with practically useful accuracy from crime scene DNA. However, our knowledge of the genetic basis of human facial structure is not advanced enough for us to reconstruct a face from DNA. For responsible use of forensic DNA phenotypic tests, it is essential that methods and validation studies are published in peer reviewed journals and are open to scrutiny."

Denise Syndercombe Court, Reader in Forensic Genetics, King's College London and EUROFORGEN researcher: "We all enjoy a good crime drama and although we understand the difference between fiction and reality, the distinction can often be blurred by overdramatised press reports of real cases. As a result most people have unrealistic perceptions of the meaning of scientific evidence, especially when it comes to DNA, which can lead to miscarriages of justice. As we developed this guide, even readers who were professionally involved in criminal justice were surprised by some of the information it contained: this particularly showed me how important the guide is in explaining science that, though complex, really does need to be widely understood."

David Bentley QC, criminal defence specialist, Doughty Street Chambers, London: "As criminal cases come increasingly to rely on DNA evidence, getting to grips with this challenging and rapidly developing topic is becoming an essential skill for the criminal lawyer to have. This excellent guide provides clear and accessible information that will help lawyers (and others) to understand both the strengths and the limitations of forensic genetics, and to be able to recognise and deal effectively with issues that may arise at trial."

Peter Schneider, Professor of Forensic Molecular Genetics, Institute of Legal Medicine, University Hospital of Cologne, Germany and EUROFORGEN coordinator: "The collaboration with Sense about Science made a big difference for us; it was positive beyond expectations. They worked smoothly and efficiently to convert very complex information into simple and straightforward messages, and instructive graphics. Continuously receiving feedback from key audiences including police, lawyers, judiciary, journalists and interested readers during this process was essential to allow the EUROFORGEN researchers to adapt the guide to make it as accessible as possible for a wide audience."

Emily Jesper-Mir, Sense about Science "It's fantastic to see researchers caring about the impact of their research has on wider society, making important information clear and accessible for those that need it - in this case from lawyers, police, judges through to potential jurors and crime fiction fans. Throughout the process, researchers listened and adapted content especially for these audiences. This is one of several public engagement partnerships we've worked on - to share sound science where there are high costs of getting it wrong. We commend EUROFORGEN for taking on this approach, and want to see more researchers involving the public to develop understandable resources."
Notes to editors

1. An embargoed copy of the guide, Making Sense of Forensic Genetics, can be downloaded: After 00.01 GMT 25th January 2017, an electronic version will be available to download:

2. European Genetics Network of Excellence (EUROFORGEN)

Making Sense of Forensic Genetics is the final output of our European Union Seventh Framework Programme funded research and networking project, which has spanned five years and ranged in expertise from forensic geneticists and social scientists to representatives of the judiciary. The European Forensic Genetics Network of Excellence will continue to exist independently from EC funding to provide information and training both to the scientific community and to the interested public. This project was financially supported from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 285487 (EUROFORGEN-NoE).

The EUROFORGEN contributors on this guide include: Professor Peter Gill, Professor Manfred Kayser, Dr Christopher Phillips, Professor Peter Schneider, Dr Denise Syndercombe Court, Dr Matthias Wienroth and Professor Robin Williams. The contributors also included Linda Geddes, Freelance science and medical writer.

3. Sense about Science

Sense about Science is an independent charity that challenges misrepresentation of science and evidence in public life. We advocate openness and honesty about research, and ensure the public interest in sound science and evidence is recognised in public debates and policymaking.

Sense about Science's public engagement team helps researchers to discuss and present research information, guided by the public and people who will use it. We draw from our extensive public networks and over a decade of working with the public on some of the trickiest issues of evidence. Our ethos is public led, expert fed, which means engaging early and directly addressing what people are thinking. These partnership projects are only available for socially or scientifically difficult issues where researchers make a convincing case that it is a matter of public interest and evidence is neglected, conflicting or misunderstood. The public engagement team includes Tracey Brown, Director; Emily Jesper-Mir, Head of partnerships and governance and Joanne Thomas, Projects and events coordinator. Contact for more details.

Our office in Brussels, which is led by Sofie Vanthournout, monitors the use and abuse of scientific evidence in EU policy. Launched in July 2016, Sense about Science EU is calling for EU citizens, researchers and the European Parliament to scrutinise and share evidence behind European policymaking.


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