Proteomics for forensic identification of saliva and vomit in a case of alleged rape.

In crime investigations, the unambiguous identification of biological traces can be decisive for framing the events. In this study, we applied proteomics to analyze scant amounts of biological residues in the context of an alleged rape case, focusing on the detection of traces of vomit. We used high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and two distinct proteomic workflows to identify proteins and possible proteolytic peptides in biological residues from clothing, bedding, and car upholstery from the alleged crime scene. Specifically, a fragment of pillowcase contained a protein pattern indicative of human saliva and a complex panel of peptides resulting from extensive hydrolysis of salivary proteins. The presence of partly digested proteins from bovine meat, wheat, and eggs, along with salivary and gastric enzymes, demonstrated the presence of vomit on the alleged victim's trousers, also providing insights into the recently consumed meal. A drop of cow's milk on the seat of the suspect's car was likely irrelevant to the criminal act. Other fabric samples showed only common contaminants, excluding significant biological traces or food-derived proteins. These findings support the judicial decision regarding consent to sexual intercourse, for which DNA individualization lacks evidentiary power, and establish a reference for annotating saliva and vomit traces in forensic investigations.
Competing Interests: Declarations. Ethics approval and consent to participate: It was not necessary to request any approval from the ethics committee since the analyses were performed at the Court’s request and authorization. The experiments reported in this study did not directly involve human subjects but were conducted on fabric fragments. Sensitive details have been omitted in the text to respect the privacy of the people involved. Furthermore, the study complies with the ethical principles for medical research involving human participants established by the Declaration of Helsinki. Competing interests: The authors declare no competing interests.
(© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.)