When forensic radiology meets ballistics – in vivo bullet profiling with computed tomography and autopsy validation: A case report

Development of a radiographic technique for porcine head ballistic research

INTRODUCTION

The porcine model shows structural features comparable to that of humans and are routinely used within research, due to the ethical, legal, and practical use of post-mortem human samples. Methods for obtaining high quality and comparable reference data using standardised acquisition protocols are essential.

METHODS

The decapitated heads of three adult white sows were subjected to radiographic imaging before and after cranial trauma (9 mm, Heckler and Koch MP5). Digital radiographs were generated using a Siemens MULTIX TOP system with an Agfa digital detector, with foam blocks and sandbags as ancillary equipment. An iterative approach was adopted by the authors to generate reproducible radiographic views from two perpendicular angles. Specimens were kept at 5 °C and wrapped in polythene bags to reduce the impact of putrefaction.

RESULTS

Standardised head radiography technique was developed for superior-inferior and lateral views demonstrating porcine anatomy. Key parameters included: automatic exposure control for tube current (∼4 mAs), tube voltage of 73 kVp, 100 cm source to image receptor distance, and an anti-scatter grid. Slight variances in specimen morphology, developmental status, and soft tissue changes did not affect imaging outcomes.

CONCLUSION

The technique and positioning proposed in this study allows for the acquisition of high quality and reproducible radiographic images for comparable ballistic research datasets. Specimen positioning and centring of the primary beam may be applied across porcine breeds, although individual radiographic parameters may differ according to equipment specifications and specimen size.

IMPLICATIONS FOR PRACTICE

Development of a reproducible radiographic technique of porcine heads in forensic and veterinary research.

CT and MRI of a transcardiac gunshot wound with an annular distribution of bullet fragments surrounding an exit-re-entrance wound after the bullet burst from a floor tile upon exiting the lying body

This case report describes medicolegal examinations of a decedent with a fatal gunshot wound. The decedent lied on the floor as a bullet was fired into his chest. Computed tomography (CT) and magnetic resonance imaging (MRI) were performed as part of the judicial investigation. The MRI examination was valuable for delineating the wound channel through the left ventricle, which was deemed the main cause for internal bleeding and fatal blood loss. The diagnostic value of CT for the detection of injuries was low in this case. However, CT allowed for the virtual investigation of bullet fragments. According to CT-based dual-energy index calculations, it could be inferred that the fragments were most likely made of lead matching .357 Magnum R-P cartridges that were found at the scene. The bullet fragments were located underneath the skin at the suspected exit wound. The exit wound was actually an exit-re-entrance wound, as it can be assumed that the fragments re-entered the body after the bullet burst from hard ground upon exiting the body of the decedent, who was lying on the floor. CT visualized an uncommon annular distribution pattern for the bullet fragments surrounding the exit-re-entrance wound. The formation of such an annular distribution pattern of bullet fragments and the relevant conclusions that may be drawn from such a distribution pattern are discussed in this article.

Heavy metal in radiology: how to reliably differentiate between lodged copper and lead bullets using CT numbers

BACKGROUND

The in situ classification of bullets is of interest in forensic investigations when the bullet cannot be removed. Although computed tomography (CT) is usually performed on shooting victims, visual assessment, or caliber measurements using CT can be challenging or infeasible if the bullets are deformed or fragmented. Independent from the bullet's intactness, x-ray attenuation values (CT numbers) may provide information regarding the material of the bullet.

METHODS

Ethical approval was not required (animal cadavers) or waived by the ethics committee (decedents). Copper and lead bullets were fired into animal cadavers, which then underwent CT scanning at four energy levels (80, 100, 120, and 140 kVp). CT numbers were measured within regions of interest (ROIs). In addition to comparing CT numbers, the dual-energy index (DEI), representing the ratio between the CT numbers of two energy levels, was calculated. The most appropriate method was applied for decedents with fatal gunshot wounds.

RESULTS

CT numbers demonstrated no significant difference between copper and lead bullets, and false classifications can easily occur. DEI calculations revealed significant differences between the two groups of bullets. The 120/140 DEIs calculated from the maximum CT numbers obtained from ROIs at the edge of copper versus lead bullets presented a significant difference (p = 0.002) and a gap between the CT numbers of copper and lead bullets and was successfully applied for the decedents.

CONCLUSIONS

This study presents a viable method for distinguishing copper and lead bullets in situ via CT and highlights the potential pitfalls of incorrect classifications.