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The Complex Bloodstain Pattern

If we were to distill down the most basic aspect of bloodstain pattern analysis, we could say that the BPA analyst attempts to classify an unknown scene pattern into one of the approximately seventeen pattern types (depending on the classification system this number may be slightly higher or lower).  In other words we have seventeen discrete boxes (spurt, castoff, impact, smear, etc.) that we try to put the scene patterns into.  This effort, when successful,  allows the analyst to understand what scene mechanisms may have led to the creation of the unknown pattern and thus allow the analyst to offer probative conclusions to the court.

As much as this is the ultimate goal, it simply is not possible in every situation.  As discussed in prior blogs, the pattern itself may be ambiguous showing only limited characteristics. Another reason that often distracts from this effort is the “complex” pattern.

Complex patterns come in two forms, conglomerate patterns and those created by highly dynamic events.

Conglomerate patterns are those in which a series of different bloodstain events deposit patterns onto the same surface.  When this occurs, depending upon the number, the area involved and the type of patterns deposited, it may be impossible to isolate within the conglomerate the individual patterns that are present.  They appear as a single pattern that doesn’t fit into any standard classification.

More problematic to the analyst is the complex pattern created by a some dynamic event. These dynamic events are far more common than one might imagine.  Some typically encountered dynamic events include drip trails in which the item dripping is simultaneously swung.  The resulting pattern may begin as a typical drip trail then suddenly transition into something resembling castoff and just as suddenly transition back to what appears as a drip trail.  Another common form is the pattern created by pressurized streaming ejections. If the orientation of the ejection to the surface is changing within a limited area the resulting pattern may demonstrate both spurt and gush characteristics that overlap and manifests itself as a single pattern.  A third common form of complex pattern occurs any time a pooling of blood deposited in the scene is impacted (e.g., a foot stomp, or hand slap), the resulting pattern may demonstrate characteristics of impact, gush and the original pooling.  In these situations, the patterns created will not fit neatly into any single classification.  Beyond these more common forms analysts also encounter highly complex patterns that are functionally impossible to classify or even begin to understand based solely on the pattern itself.

How does one respond to the complex pattern?  First, recognize that they exist.  Accept them for what they are and do not attempt to isolate them into a single classification. 

When presented with conglomerate patterns, detailed study may ultimately allow the analyst to isolate the inter-mixed patterns, but there is no guarantee of this.  In terms of the more common forms of dynamically produced patterns (those described above), despite their complexity the analyst will generally understand the nature of the creation mechanism.  But when presented with highly dynamic events, the resulting pattern may never be fully understood.  In these instances the best the analyst can do is to describe any and all characteristics in the pattern.  If sufficient investigative context is present (which may include testimonial evidence) some limited explanation may be possible.  Lacking such context, these patterns may remain a mystery precluding any conclusions by the analyst. 

When presented with complex patterns, remember to never force a classification and stay objective when offering any conclusions. Some patterns simply cannot be explained in a given scene context.