Bloodstain Pattern Analysis & Bayes
Publication - July 2023
The findings from a bloodstain pattern analysis (BPA) may assist in formulating or falsifying scenarios that are considered during the investigative stages of a criminal investigation. When a case proceeds to trial, the bloodstain pattern expert may be asked about the relevance of their findings given scenarios proposed by the prosecution and defense counsel.
Relevance of Expert Opinions
Such opinions provided by an expert are highly relevant to police investigations or legal proceedings. However, the reasoning behind the opinion or implicit assumptions made by the expert may not always be transparent.
Evaluation Framework in Forensic Science
A proper framework for the evaluation of forensic findings has been developed since the late twentieth century. This framework is based on the hierarchy of propositions, Bayesian reasoning, and a model for case assessment and interpretation. When implemented in casework, it mitigates some of the risks of cognitive biases and makes the reasoning and scientific basis for the opinion transparent.
Application Across Forensic Disciplines
This framework is broadly used across forensic science disciplines. In this paper, we describe its application to the field of Bloodstain Pattern Analysis, using a case example from the Netherlands Forensic Institute (NFI).
Authors
- Leon Meijrink
- Mikle van der Scheer
- Bas Kokshoorn
Forensic Trace Dynamics research group
Thanks to new methods of analysis, it is now possible to detect even the smallest traces left behind at a crime scene or carried away by the suspect. What can this tiny, often hard-to-detect trace evidence tell us about the precise details of an event? This is the central question of the Forensic Trace Dynamics research group.