Journal de médecine légale

Crime Scene Investigations of Forensic DNA-Analyses

Abstract

Charles Tieche

In Switzerland, burglaries rank as the top mass crime according to forensic DNA analysis. In the Swiss DNA database, almost one-third of the DNA trace profiles are connected to burglaries. However, it is unknown if the DNA sampled during the collection of prospective DNA traces within a person's home during a burglary came from the culprit or from a resident of that home. Crime scene investigators typically do not gather reference samples from all the homeowners due to the high frequency of burglaries for administrative and financial reasons. As a result, it must be considered that there is a significant likelihood that a DNA profile from someone who was allowed to be at the crime scene will ultimately be transmitted to a DNA database for comparison. As far as we know, no research has been done to determine the proportion of these non-perpetrator profiles that end up in DNA databases. We gathered reference samples from locals who had recently experienced house invasions to help answer this question. We are able to demonstrate that the bulk of the DNA samples gathered during burglary investigations belong to the inhabitants by contrasting the profiles created from these reference samples with the profiles created from trace DNA. We further demonstrate that trace DNA collection in the vicinity of the break and entry area, in particular window and door glasses, is most promising for sampling perpetrator instead of inhabitant DNA, despite the small number of cases included in the study, likely due to a crime decline caused by the pandemic.