Crime Scene Investigator Network Newsletter

Introduction
To the layman, experts appear to act on instinct. This is true when listening to a classical pianist perform a complicated piano concerto, and this is no less true when listening to an experienced crime scene reconstructionist recite his or her conclusions regarding a complicated bloodstain pattern analysis without a supporting explanation. Although the layman understands that education, training, experience, and practice are all necessary to reach any degree of expertise, it is still difficult for him to comprehend exactly how all that background ends up synthesized into the final result. This difficulty is also shared by jurors, judges, and attorneys, and unfortunately, can result in questioning the scientific validity of some forensic disciplines. Furthermore, this problem of not fully understanding the steps that will ultimately lead to a valid scientific conclusion does not lie solely with those outside the forensic community. Many qualified experts in bloodstain pattern analysis will be able to come to complicated conclusions quite accurately, but may have trouble explaining just how they arrived at their results. These experts are most likely following a scientific methodology; however, they may never have stopped to think exactly what that methodology is.

The recent attacks on the validity of latent print identification have prodded the latent print community to examine in detail just exactly how and why identifications are made. As a result, the discipline of friction ridge identification has grown stronger and its examiners more confident in their conclusions. This article attempts to lay out a discrete bloodstain pattern analysis methodology that can be articulated to judges and attorneys to dispel any questions about the lack of scientific validity in the discipline.

The Scientific Method
One way to show that a forensic discipline is based upon sound scientific principles is to show that it conforms to the scientific method. It would seem simple enough, then, to write down the steps in the scientific method and then show a correspondence between these steps and the steps involved in the discipline in question. However, if one begins researching to find out just what those steps are, one discovers rather quickly that there is no single accepted version of the scientific method. Depending upon the source, the scientific method consists of as few as four steps or as many as eleven. Furthermore, there are dissimilarities both in the names of the steps and in the sequence in which they are to be carried out.

It is important to note, then, that a single scientific method does not exist, at least not as a standard list of steps that are common to all areas of science. And therein lies a major problem regarding the legal view of various forensic disciplines, to include that of bloodstain pattern analysis. Henry H. Bauer tells us, “So long as science is viewed as monolithic, founded on the scientific method, it is possible (and therefore irresistibly tempting) to label some sciences, or some bits of science, as ‘more scientific’ than others, according to the degree to which the method has been or can be successfully deployed.” Indeed, bloodstain pattern analysis has been attacked in court as being one of those “lesser” sciences or, worse yet, as a so-called pseudoscience.

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