Misleading DNA Evidence: Reasons for Miscarriages of Justice

Every criminal lawyer needs to read Peter Gill's "Misleading DNA Evidence: Reasons for Miscarriages of Justice" (Academic Press, 2014).Judges should read it too. It is admirably clear and no expertise is required of the reader. If you have some experience with DNA evidence and Bayesian reasoning you will still find the book useful for its descriptions of how things can go wrong.Peter Gill is one of the leading experts on forensic DNA. What he has to say is well worth attention.Things can go wrong (as I so eloquently put it above) because DNA detection is now very sensitive and DNA is everywhere. A typical crime scene will have detectable amounts of DNA from many sources. Partial DNA profiles can be detected too, and this complicates the evaluation of mixed samples. Investigators can contaminate a crime scene, transferring DNA from one thing to another, with even latex gloves being vehicles for transfer. Detection of DNA does not mean that it is necessarily present because it was in a body fluid present at a crime scene. Samples collected for analysis must be sealed, and gloves changed, so that no transfer should occur between them, and in the laboratory the risk of transfer between suspect and scene samples must be minimized. There should be studies of the risks of contamination within a laboratory, and these should be done without the knowledge of those who work in that laboratory.Courts tend to leap to conclusions that are not scientifically sound. Inferences that could be tested experimentally are often drawn without that evidence. A common example may be the assumption that a defendant's DNA on a murder weapon found at a crime scene was only on the weapon and was not also on a number of other items which would innocently explain why it was also on the weapon; what the media refers to as the Amanda Knox case is an illustration that Dr Gill uses to make this point: the defendant's DNA on a knife, allegedly the murder weapon, in a kitchen drawer, was given significance it may not have deserved in the absence of evidence of whether her DNA was also on other items in the drawer (which it surely would have been as she used the kitchen).The Kindle app version is very well produced, giving coloured text, with links that are easy to navigate, including links to some of the cited technical papers that are available online. It is a book that should be discussed with expert witnesses, whether they are relied on by the prosecutor or by the defendant.

As a protein biochemist who has taken an interest in DNA and blood forensics in the last five years, I waited for publication of this book with hopes that it would be interesting and information. The book well exceeded my expectations. Professor Gill’s discussion of the four levels of evidence (section 1.7) alone would make me glad I purchased this book. He also discusses errors in the ways that forensic scientists frame opposing hypotheses very clearly in the Scott and Cleobury cases. He also discusses the Farah Jama case and the “excellent” Vincent report that cleared Jama, despite the precise mechanism of contamination being unknown. The Scott case also demonstrates that DNA in a negative control is sometimes ignored by the lab.Chapter 5 is devoted to the prosecution’s errors in the Amanda Knox/Raffaele case. His criticism of an absurd inference about a knife from Sollecito’s flat is complemented by an explanation of how the prosecution could have tested its hypothesis. He does the same thing with respect to the paradox of the presence of a tiny amount of the victim’s DNA that might have been on the knife with the complete absence of blood. My only criticism of this book is that it is too short.

The book details the story behind one of the most well know cases to lawyers who defend those accused of crime - People v. Molineux, the New York case that set the standard for understand when other bad acts are admissible. A required red for those who are interested in this case. Well researched with some surprising connect to the politics of the 1970's. You will have to read it to find out this connection.

This book is a must read for any person in the field. Lawyers and forensic scientists need to take this sort of sceptical approach on board to undo the false notions engendered by trashy programs such as CSI.

Full of good information.

Very inciteful. It is useful in addressing the fallacies engaged in by both prosecutors and defense attorneys. DNA is not the be all end all in a criminal case.

Interesting idea, but not very well written.

Very good for a forensic scientist