On websites such as mumsnet and money-saving-expert, discussion forums are dedicated to the difficulty of removing lily pollen from carpets, clothing and tablecloths.

The solutions range from dabbing with Sellotape and soaking in vinegar to rushing to the dry cleaners. But the stubbornness that makes the orange pollen stains a household nuisance is the same property which forensic science has begun using to fight gun crime.

Scientists have perfected the technique of “tagging” bullets with microscopic specks of pollen from the oriental lily (Lilium orientale) and the white trumpet lily (Lilium longiflorum) which will stick to the hands of anyone who handles them.

The research team is now extending its work to see if the “nanotags” can also be attached to knives.“It’s a new type of flower power,” said Paul Sermon, of the University of Surrey, who led the research. “The tags primarily consist of naturally occurring pollen, a substance that evolution has provided with extraordinary adhesive properties.

“Each cartridge would have between 1,000 and 1 million tags on it, and if you touch one you will end up with a large number of those on your hands, gloves or clothes. They are almost impossible to get off and they don’t degrade over time.”

The tags measure 30 microns (or millionths of a metre) in diameter and are invisible to the naked eye. But they can be picked up by swabs and microscopes and link someone who had handled ammunition to bullet casings found at the scene of a shooting.

At present DNA is recovered from only 10 per cent of bullet casings recovered. The heat generated by firing the bullet destroys DNA and the copper content of brass cartridges causes traces to decay.

In addition to the pollen, cartridges would also be coated with a slightly abrasive chemical coating which would strip off tiny skin fragments of anyone handling it. This would increase the chances of DNA being retained on the cartridges.

The coating and tags could be altered between batches of bullets and manufacturers to ensure that cartridges would have a chemical signature. Professor Sermon, whose research was funded by the Engineering and Physical Sciences Research Council, added: “We’re currently focusing on understanding the precise requirements of the police and cartridge manufacturers. Police forces are quite excited. This work could make a valuable contribution not only to solving gun crime but also to deterring criminals from resorting to the use of firearms in the first place. The next stage is to see if the technique can be applied to knives.”

The technology could be in use within a year, but its usefulness in detecting crime will require a major diplomatic effort by ministers to persuade other countries to require their ammunition manufacturers to use it.

Most of the 9mm ammunition recovered by police units is manufactured overseas. Criminals have also resorted to making their own bullets.

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