Using Objective Criteria for Bloodstain Pattern Classification

This webinar originally occurred on August 1, 2024
Duration: 1 hour

Overview

The science of bloodstain pattern analysis evaluates bloodstain patterns present at a scene or on various objects, for the purpose of interpreting patterns in the context of the scene and issuing various opinions. As outlined in the OSAC-proposed standard “Methodology in Bloodstain Pattern Analysis,” analysts issue two categories of opinions – classification of the bloodstain patterns themselves and event reconstruction interpretations. As described: “Classification of bloodstains and bloodstain patterns is the process that utilizes observable characteristics to include those mechanisms that cannot be excluded, resulting in an interpretation.” Further refinement of the initial classification can occur based on case-relevant information.

Starting with the Scientific Working Group on Bloodstain Pattern Analysis (SWGSTAIN) in 2009 and followed up with the Academy Standards Board (ASB) in 2017, the bloodstain community established standard terms and definitions for basic pattern types. This was a significant step forward. However, definitions only explain the process to create specific patterns. The current definitions for these pattern types do not detail the specific features present that can be used to assist in the classification step. Proper classification is based on the features present within the pattern and not based on definitions.

This webinar will guide the analyst through the process of establishing objective criteria of what features must be present to include specific pattern types within the classification step of the methodology. These objective criteria will be rooted in concepts of fluid dynamics and will account for variations within the pattern creation processes and the effects of target surfaces. The webinar will use the biological classification of organisms as an example of how visual features are used to guide biologists. In some situations, different mechanisms can create patterns with very similar features. The objective criteria must recognize these situations and take them into account. The webinar will describe an elimination-based approach for pattern classification and how it embraces the concept of qualitative uncertainty in bloodstain pattern classification. 

Detailed Learning Objectives

1. Attendees will understand the common errors associated with using definitions of pattern types rather than features to guide pattern classification. 
2. Attendees will understand how to develop objective features of bloodstain patterns to guide classification using concepts from fluid dynamics and specific aspects of the pattern formation mechanisms. 
3. Attendees will understand how an elimination-based approach to pattern classification accounts for concepts of qualitative uncertainty in pattern classification. 

Presenter

• Jeremiah Morris | Forensic Scientist Supervisor, Crime Scene Investigation & Technical Leader in Bloodstain Pattern Analysis, Johnson County Sheriff’s Office Criminalistics Laboratory