Fatal dog attacks represent a significant forensic challenge, requiring reliable canine genetic identification from complex biological mixtures containing both victim blood and canine saliva. The evidential value of canine DNA profiling in homicide investigations depends critically on accurate species specificity amplification and interpretation in mixed-species samples. Therefore, comparative evaluation of available STR panels is essential to identify systems suitable for forensic casework involving human–canine DNA mixtures.

We report a homicide investigation from Naples, where a victim was fatally attacked by a dog. Swabs collected from bite wounds contained mixed biological material consisting of human blood and canine saliva. DNA extracts were amplified using two commercial STR kits (Thermo Fisher Scientific Canine Genotypes™ Panels 1.1 and 2.1) and the CaDNAP 13-STR panel.

The CaDNAP panel, previously validated for forensic canine identification, produced a complete and interpretable genetic profile of the dog, showing no human-derived STR profiles. In contrast, both Thermo Fisher panels exhibited significant interference in the mixed samples, including drop-in peaks not observed in control profiles. These artifacts compromised profile interpretation and reduced statistical reliability.

The CaDNAP system demonstrated superior performance across the high species specificity - with no detectable cross-amplification of human DNA - and the robust discrimination of the canine contributor. Conversely, the commercial kits showed lower specificity and increased susceptibility to mixture-related artifacts, potentially leading to erroneous interpretations.

This casework highlights the critical importance of employing forensically validated canine STR panels in complex human–animal mixtures. The results demonstrate that not all commercially available systems are suitable for forensic applications, particularly in high-stakes scenarios such as homicide investigations.

These findings emphasize the need to increase international awareness and adoption of standardized, validated STR systems, such as CaDNAP. Greater participation of laboratories in proficiency testing schemes and continued methodological harmonization are essential steps toward building reliable global canine allele frequency databases. Such efforts will ultimately strengthen the statistical weight, reproducibility, and admissibility of canine DNA evidence in forensic science.

Authors

• Aldo Di Nunzio (Forensic Genetics Laboratory, CEINGE Advanced Biotechnology Franco Salvatore; Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Italy)
• Fernanda Iafusco (Forensic Genetics Laboratory, CEINGE Advanced Biotechnology Franco Salvatore, Italy)
• Michele Di Nunzio (Forensic Genetics Laboratory, Legal Medicine Unit, University of Barcelona, Spain)
• Nicholas Iacovelli (Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Italy)
• Ciro Di Nunzio (Forensic Genetics Laboratory, CEINGE Advanced Biotechnology Franco Salvatore, Italy)
• Nadia Tinto (Forensic Genetics Laboratory, CEINGE Advanced Biotechnology Franco Salvatore; Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Italy)