Abstract
In molecular ballistics, where traces originating from the use of firearms against biological targets are investigated, “backspatter” traces are of particular importance. This biological material comprising blood and tissue from the victim is propelled back from the bullet entry site towards the direction of the shooter and can consolidate and persist on the inner and outer surfaces of the firearm, from where it can be collected and analyzed. Thus, a connection between the weapon and the victim can be established solely by molecular biological trace analysis. For the criminalistic investigation of gun-related crimes, the determination of the distance between the weapon and the victim can be of critical importance in reconstructing the circumstances of a crime. In this study, we investigated possible correlations between the shooting distance and the amount of backspatter in/on the used firearm. To this purpose, we employed a previously established skull model and performed shootings in triplicates from various distances up to 50 cm with two types of handguns (pistol and revolver). Backspatter was collected from various sampling locations, and DNA contents were quantified. A post-shooting wound channel evaluation was conducted by optical and radiological evaluation. The obtained DNA yields varied considerably between replicates from the same and from different distances. In contrast, apart from contact shots, no meaningful differences were observable in wound channel evaluations. In summary, no meaningful correlation between backspatter distribution and DNA yields, the shooting distance and the condition of the wound channel could be established.
Highlights
IntroductionThe application of molecular biological analysis of backspatter traces to estimate the shooting distance and/or discriminate between distance categories would provide an additional tool to support the objective, evidence-based reconstruction of the events that took place at a crime scene
In forensic criminalistic casework, it is essential to detect and interpret the traces and trace patterns at a crime scene, which includes trace material on the body of persons or on objects that are or might be connected to the circumstancesElectronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Int J Legal Med (2020) 134:1619–1628 direction of the firearm and shooter [4]
The large variability observed in our dataset strongly indicates that the inference of the shooting distance from amounts of backspatter recovered from different firearm surfaces will be associated with a large uncertainty, and it remains to be seen if such an approach could mend the risk of misinterpretation for isolated real case scenarios
Summary
The application of molecular biological analysis of backspatter traces to estimate the shooting distance and/or discriminate between distance categories would provide an additional tool to support the objective, evidence-based reconstruction of the events that took place at a crime scene. These analyses include quantitative evaluation of nucleic acids in backspatter traces recovered from outer and inner surfaces of the firearm. They detected traces of backspatter inside of firearms with sufficient amounts of nucleic acids to enable successful analysis of samples from up to 15- (DNA) and 30-cm (RNA) shooting distances
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