Patterns of injury – an evaluation

Abstract

The concept of ‘pattern of injury’ is used in a number of different ways in forensic medicine. The Oxford English Dictionary defines a pattern, in the sense being used here, as ‘a typical instance; a signal example’. In forensic pathology, the concept underpins conclusions that the death belongs in a particular category, e.g., accident versus homicide; in the case of a body found by the road side, the pattern of injury we associate with pedestrians killed by motor vehicles differentiates the death from one due to blunt force assault. In some cases, we cannot assign the death to one category or other because the strength of the pattern is insufficient to distinguish between the two. We also use the concept to describe how we believe a subset of injuries in one deceased might have been caused. For example, defence wounds in a case of homicidal stabbing. More specifically, we use the concept to describe in general terms how a single injury might have been caused, for example, a tramline bruise. Finally, and very specifically, we sometimes use the concept of ‘pattern of injury’ to describe the individualisation of a particular injury to a particular object, for example, the pattern from the sole of a trainer shoe on the deceased’s forehead linking the injury to a particular shoe, or brand of shoe. The multiplicity of uses of the one phrase must be confusing for the trainee and we should distinguish between them. Leaving these definitional issues to one side, there is a threshold issue of whether a pattern (in one or other of the above circumstances) actually exists. We have no data base, no evidential framework in forensic medicine to help us here. The knowledge base is simply descriptive, and varies considerably depending on the context and circumstances. How dowe decide that the threshold has been reached; that a pattern actually exists? If we think a pattern exists, what properly follows from that? This is actually a very large topic. For the purposes of this presentation, it is illustrated by reference to a conviction largely based on forensic medical evidence about the ‘pattern of injury’ in three homicides by stabbing in one incident. The prosecution successfully contended that the pattern of injury was similar in all three and that this meant there was one killer; the defence position was that this was not the case, and that there were two people responsible for the deaths.