Challenging Forensic Science: How Science Should Speak to Court

This first week will set the scene for the course. You will meet the instructors; learn about their background, teaching, research and casework activities. The School of Criminal Justice (University of Lausanne) will be shortly presented through a virtual visit, followed by the course objectives. The recent ENFSI guideline for evaluative reporting, used throughout the course, will be presented. ENFSI stands for the set of the good principles for writing forensic reports to be used in a court of law. The whole course aims at contrasting the practice as observed in notorious cases with the good practice promoted by the ENFSI guideline. Hence, we will start by setting out some reporting criteria that are essential to bring reliable evidence in court and explain the principles of interpretation (based on the concept of likelihood ratio) that should govern the production of any forensic evidence. The application of these principles leads to a defined way whereby the forensic scientist is entitled to speak to court.

There is a general misconception that a piece of forensic evidence is sufficient to clinch the outcome of a case. This module aims at showing that the reality is more subtle and is intrinsically linked to the concept of hierarchy of propositions. Cases based on DNA and gunshot residue (GSR) evidence will be analysed and discussed. First, through the Weller case we will demonstrate the DNA findings providing information towards the source of the DNA may not be at the core of the issue in the case. More and more the source of the DNA is not challenged, but how the DNA got there is.

Based on international cases (Knox, Jama, Anderson and Scott) we will illustrate the potentials aspects that one needs to consider when assessing the value of DNA found in small quantity. You will be shown how one performs DNA analysis and what type of results can be produced. We will apply the ENFSI and the ISFG guidelines for evaluative reporting in the case at hand and see if the principles advocated allow avoiding misleading evidence. We will compare the situations where large quantities of blood are found to cases where low template DNA is recovered. You will learn to contrast these two situations and discover what type of results can be expected and what methods allow a balanced and robust interpretation. This first part of the course will demonstrate that very sensitive techniques require robust interpretation methods. In the second part of the course, you will understand that with trace quantities, stringent control procedures are needed on the crime scene and in the laboratory. Indeed, pollution (or so-called contamination) is an aspect one needs to take into account. Cases (for example in Australia, the USA and England) have shown that the traces from the crime scene can be polluted at the hospital, by paramedics or in the laboratory. It is thus essential to consider this possibility, especially when DNA is the central (and only) element supporting the allegation of a person’s involvement in a crime. How to take into consideration the possibility of error/contamination when assessing the results will be presented.

This week will be dedicated to how forensic scientists should convey the value of their results. From our white room dedicated to photography, we will study famous cases - including the Dreyfus case- and see how statistics can be misused. It will allow us to discuss how statistical values ought to be presented in court. A statistician (Phil Dawid) and a legal scholar (David Kaye) will be interviewed. The second essential topic we will present will be on fallacious reasoning, and in particular on what has been coined, more than thirty years ago, the prosecutors fallacy. Bill Thompson, the first to have described this fallacious argument used in court will be another of our guest interviewees.