Wound ballistics and the unusual injuries of the tandem bullet phenomenon: A systematic review of case-specific characteristics

This study revisited the forensic literature to compile case-specific characteristics of the tandem-bullet phenomenon (TBP). A systematic review was performed following the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) and The Joanna Briggs Institute's manual. The protocol was registered in Open Science Framework. Ten primary databases and two sources of grey literature were searched, with descriptive studies on TBP, with information about the victim, weapon, ammunition and injuries, being included. From an initial sample of 2360 studies, 13 were eligible. The studies reported 11 male and 2 female victims, with ages between 14 and 63 years (mean = 39.45 ± 14.51 years); seven were victims of suicide (or suicide attempt); most of the victims (69.23%) were shot in the head and neck; and most (84.61%) had an entry and exit wound ratio of 1:0, respectively. The use of image exams to assess injuries and bullets was reported in 12 cases (92.30%). The most frequent reasons for the TBP were the mismatch between weapon and ammunition and the use of defective cartridges (76.92%). Forensic professionals must be aware of the case-specific characteristics of the TBP to overcome confounding factors in wound ballistics and medicolegal examinations.