Pollen-coated bullet could make its mark on criminals

2019-03-02 08:08:09

By Barbara Axt (Image: EPSRC) Pollen and grit are the components of a new coating for gun cartridges that UK researchers hope will help to identify criminals that use firearms. Under their scheme, batches of cartridges would be labelled with unique “nanotags”, invisible to naked eye, designed to attach themselves to hands, gloves and clothing of anyone that handles a cartridge. Some of the tags would remain on the spent cartridge casing. The tags could perform a similar, but more authoritative role to the specks of unintended explosives residue sometimes used to tie people to guns or crimes. The nanotags are made from pollen, and a mix of grains of crystal oxides such as zirconia, silica and titanium oxide. Using varying combinations of crystal and pollen grains, it is possible to make large numbers of unique tags. “We decided to work with pollens because they have a unique structure, resistant to temperature and easily recognisable,” said Paul Sermon from the University of Surrey, who has led the research. “It’s also easily dispersed and carried around in clothes, skin, etc.” Pollen grains (see image, right) vary between plant species and are easily identified under a microscope. Chemical techniques could reveal which oxides were mixed with the pollen, and in which proportions to work out which batch of cartridges they originate from. “The most challenging part of the project was nanoengineering a coating robust enough to withstand the [high temperatures of] firing and that would still release the tags when touched,” he added. Sermon says that the tags are designed to be compatible with current cartridge manufacturing processes and could be implemented within 12 months of companies or government supporting their introduction. In addition to the tags, the researchers are working on a way to have gun cartridges retain skin cells from anyone that handle them, for later DNA-based forensic analysis. Micro-scale grit can effectively trap cells and protect DNA from the heat of firing. Today, cartridges are smooth and rarely retain DNA or fingerprints. The team is also looking to apply that technique to knives so they retain DNA more reliably. The tags were developed by researchers from Brighton, Brunel, Cranfield, Surrey and York Universities, with commercial collaborators including UK defence firm BAE Systems. Forensic Science – Keep up with the pace in our continually updated special report. More on these topics: