Problems of Forensic Sciences 2008 Vol. 73 (LXXIII) 70-81
THE EVIDENTIAL VALUE OF TRANSFER EVIDENCES – A HIT-AND-RUN ACCIDENT
Grzegorz ZADORA, Beata M. TRZCIŃSKA
Institute of Forensic Research, Krakow, Poland
Streszczenie
In this paper the usefulness of the likelihood ratio framework as a basis for thinking and reaching conclusions about evidence values has been presented on the basis of casework in which a pedestrian was hit by a car which fled from the accident scene. The pedestrian died and the suspected car was found some hours after the accident and suitable control samples were collected. Performed analysis showed compatibility of physico-chemical features between evidence and control material such as paint, glass, plastic and fibres. A way of thinking based on the likelihood ratio approach (LR) was applied in reaching the final conclusion. The framework is useful as a guideline for experts, forcing them to address the right questions and hypotheses (not only the hypothesis of the prosecution, but also alternative (defence) hypothesis(es)). This way of thinking, which is based on LR, has great merits even if a numerical value for LR cannot be calculated due to lack of adequate data, as is often the case. Moreover, the LR approach can also be used to draw conclusions about the evidential value of a combination of different kinds of forensic evidence. This approach allowed us to provide extremely strong support for a hypothesis that traces of paint, glass, plastic and fibres recovered from a victim’s clothes originated from the suspected car, which should effectively enable the judge to issue a correct verdict. This casework was also interesting in that a two-colour paint smear (two adjacent layers of car paint) was found on the victim’s trousers, which is not a very common situation.
Słowa kluczowe
Forensic science; Likelihood ratio approach; Hit-and-run accident; Transfer evidences; Physico-chemical analysis.