Research Student: Rick Graham
Jury interpretation of DNA evidence presented in court
DNA profiling has been revolutionary for forensic science, allowing the comparison of biological samples left at the crime scene with that of suspects.
New developments allow profiles to be generated from ever smaller crime scene samples. However, the very sensitivity of these techniques has caused difficulties in terms of their use in evidence. Human error, contamination of samples and other factors all serve to complicate the evidence presented to the court.
Furthermore, the evidence is presented in statistical form. The "Prosecutor's Fallacy" is the name given to the way in which results have sometimes been presented. A match probability of, say, 1 in 20 million has been equated by expert witnesses with the statement that there is only a 1 in 20 million chance of the accused being innocent: a false reasoning. In fact, there is a high probability that someone shares the same DNA.
My research is into the ways in which the jury understands and interprets DNA evidence in court; it is essential that they do this correctly if they are to reach a proper verdict.
It has been argued that most cases involving DNA do not reach a jury either because of a guilty plea or because the case is heard before magistrates. However, it is essential that the entire judicial system as regards DNA evidence is shown to be robust, both for public confidence and to avoid miscarriage of justice.