“Articulating a Concise Scientific Methodology for Bloodstain Pattern Analysis”


Journal of Forensic Identification
Vol. 55 No. 4 July/August 2005

“Articulating a Concise Scientific Methodology for Bloodstain Pattern Analysis”

There have been an increasing number of challenges in our court system encompassing many areas of forensic science. It is more imperative now to be as articulate as possible in describing a methodology for any forensic discipline. Therefore many forensic scientists are re-examining their methods of explaining analyses.

This article attempts to describe a bloodstain pattern analysis in a way that judges and attorneys can understand, in an attempt to decrease the questioning of its scientific validity. Although Bloodstain Pattern Analysis is considered a “pseudoscience” and less scientific than other areas of science, there are some basic and accepted scientific principles that can be identified when examining the process of “B.P.A.”. The methodology typically used has eight steps, which falls in the range of four to eleven steps in a scientific method. In this forensic discipline there is not one single or definite method used, however simply by following a method shows that they are based on solid scientific principles.

The eight-step method described in this article is as follows:
1-Data collection
2-Case review
3-Isolation /Description of patterns
4-Formulation of hypothesis
5-Testing of hypothesis
6-Formulation of theories
7-Testing of theories
8-Conclusion and results

Although the data collection is extensive, it may include photos of the crime scene and it’s victims, lab and autopsy reports, witness interviews with rough sketches and all physical evidence, once you proceed to step three all blood stain patterns which were collected are isolated and analyzed objectively with no attempt to infer any meaning until all testing is done.

In my opinion this is a challenging subject to try and articulate to judge and jury, because there can be so many scenarios resulting from all the patterns and theories tested. It is few and far between when a bloodstain analyst can come up with a single definitive scenario that can explain everything. When you have one or more “what ifs” it lessens the credibility of your testimony. I think they should focus on the facts being that most cases can provide definite elimination or exclusion of particular scenarios, which is valuable information when validating either the prosecution’s or defense’s case. Therefore, the conclusion given is the most likely scenario based upon the evidence and testing done.

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