Determining The Location of an Impact Site from Bloodstain Spatter Patterns: Computer-Based Analysis of Estimate Uncertainty.

The estimation of the location in which an impact event took place from its resultant impact spatter bloodstain pattern can be a significant investigative issue in the reconstruction of a crime scene. The bloodstain pattern analysis methods through which an estimate is constructed utilise the established bloodstain pattern analysis principles of spatter bloodstain directionality, impact angle calculation, and straight-line trajectory approximation. Uncertainty, however, can be shown to be present in the theoretical definition and practical approximation of an impact site; the theoretical justification for impact angle calculation; spatter bloodstain sample selection; the dimensional measurement of spatter bloodstain morphologies; the inability to fully incorporate droplet flight dynamics; and the limited numerical methods used to describe mathematical estimates. An experimental computer-based research design was developed to investigate this uncertainty. A series of experimental impact spatter patterns were created, and an exhaustive spatter bloodstain recording methodology developed and implemented. A computer application was developed providing a range of analytical approaches to the investigation of estimate uncertainty, including a three-dimensional computer graphic virtual investigative environment. The analytical computer application was used to generate a series of estimates using a broad spatter bloodstain sampling strategy, with six potentially probative estimates analysed in detail. Two additional pilot projects investigating the utility of a sampled photographic recording methodology and an automated image analysis approach to spatter bloodstain measurement were also conducted. The results of these analyses indicate that, with further development, the application of similar analytical approaches to the construction and investigation of an estimate could prove effective in minimising the effect that estimate uncertainty might have on informing the conclusions of this forensic reconstructive process, and thereby reaffirm the scientific expert evidential status of estimate techniques within legal contexts