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.