A new method was used to study the dispersion of lead particles from hunting bullets – the result surprised the researchers

Lead is toxic to animals and humans even in very small concentrations. The use of lead shot in hunting in wetland areas and their buffer zones has been prohibited since February 15, 2023. Lead-free, expanding bullets and hunting cartridges have been readily available for a couple of decades and have become more common, especially in the past ten years.

Using medical imaging, the researchers examined how distinctly the wound channels created by lead-containing and non-toxic bullets differ from each other. Gelatin blocks are typically used for studying bullets, and the analysis of wound channels and bullet fragmentation has mainly been done visually in the past. In computed tomography, metal residues are better distinguished than in traditional methods of examination.

The comparison revealed that small lead fragments spread more widely than previously estimated, even though the overall amount of lead residue left by the bullets is relatively small. The same amount of lead is found in a single larger lead pellet.

"The research results were somewhat surprising. The full metal jacket bullet, which was thought to remain intact, fragmented in the gelatin and left behind numerous lead fragments. The expanding bullet containing lead also left behind a significant amount of lead fragments. The quantity of fragments and their distribution throughout the entire wound channel was surprising. The non-toxic hunting bullet left only a single loose piece in the wound channel, and it didn't contain any lead. The differences between ammunition types were clear," says the leading researcher, Associate Professor Juho-Antti Junno.

When a lead bullet fragments, its pieces can spread wider and potentially produce more meat damage more than a non-toxic alternative. However, according to Junno, this effect is minimal.

The researchers believe that in forensic investigations, gunshot injuries caused by lead-free bullets will likely be encountered, and using computed tomography, the ammunition type can be determined by studying the shape of the wound channel and the pattern of lead residue left by the bullet.

The study used three different types of cartridges. One represented full metal jacket bullets, which are expected to remain intact and unchanged upon impact. The other two cartridges were equipped with expanding bullets suitable for deer hunting, for example. One of the expanding bullets contained lead, and the other was a non-toxic full copper bullet.

The research has been published in the International Journal of Legal Medicine.