Skip to content

Using the Likelihood Ratio in Bloodstain Pattern Analysis

Journal: Journal of Forensic Sciences
Published: 2021
Primary Author: Daniel Attinger
Secondary Authors: Kris De Brabanter, Christophe Champod

There is an apparent paradox that the likelihood ratio (LR) approach is an appropriate measure of the weight of evidence when forensic findings have to be evaluated in court, while it is typically not used by bloodstain pattern analysis (BPA) experts. This commentary evaluates how the scope and methods of BPA relate to several types of evaluative propositions and methods to which LRs are applicable. As a result of this evaluation, we show how specificities in scope (BPA being about activities rather than source identification), gaps in the underlying science base, and the reliance on a wide range of methods render the use of LRs in BPA more complex than in some other forensic disciplines. Three directions are identified for BPA research and training, which would facilitate and widen the use of LRs: research in the underlying physics; the development of a culture of data sharing; and the development of training material on the required statistical background. An example of how recent fluid dynamics research in BPA can lead to the use of LR is provided. We conclude that an LR framework is fully applicable to BPA, provided methodic efforts and significant developments occur along the three outlined directions.

Related Resources

Extracting Case-Specific Data from Validation Studies

Extracting Case-Specific Data from Validation Studies

This CSAFE webinar was held on May 10, 2022. Presenters: Steve Lund Statistical Engineering Division, NIST Hari Iyer Statistical Engineering Division, NIST Presentation Description: The legal and scientific communities agree…
Shining a Light on Black Box Studies

Shining a Light on Black Box Studies

This CSAFE webinar was held on April 22, 2022. Presenters: Dr. Kori Khan Iowa State University Dr. Alicia Carriquiry Iowa State University Presentation Description: The American criminal justice system heavily…
Sampling for Forensic Practitioners Short Course

Sampling for Forensic Practitioners Short Course

This three-session short course took place on March 25, April 1, and April 8, 2022. Recordings of completed sessions and practicum materials can be found below. Presenters: Alicia Carriquiry Director…
Modeling And iNventory of Tread Impression System (MANTIS): The development, deployment and application of an active footwear data collection system

Modeling And iNventory of Tread Impression System (MANTIS): The development, deployment and application of an active footwear data collection system

This CSAFE webinar was held on March 24, 2022. Presenters: Dr. Richard Stone Iowa State University Dr. Susan Vanderplas University of Nebraska, Lincoln Presentation Description: This webinar details the development,…