In an effort to crack down on robberies at McDonald’s in Sydney, the company has hired a British security firm to install a system that sprays a “non-toxic solution with DNA Code” on would-be thieves on their way out the door of the fast-food outlets.

“A spokesperson for McDonald’s said the company will increase the use of ‘SelectaDNA‘ in stores all over the country after a successful trial in their six busiest Sydney restaurants was launched in January last year,” The Sydney Morning Herald reported. ”The move comes as police ramp up their patrols of local McDonald’s restaurants after a spate of robberies across Sydney during the Christmas and New Year period.”

The Intruder Spray solution contains a UV tracer and a unique DNA code, linking them irrefutably to the crime scene, says the SelectaDNA’s website. To date, it has installed 13 Intruder Spray security systems in McDonald’s across Australia.

Police are able to find SelectaDNA by using a UV Torch. The spray glows bright blue under UV light.  By DNA Analysis, an offender can be linked to the premise, said ABC News. A sample the size of a pinhead is all that is required to link an offender to the site.

Once triggered by a thief, the spray will fall onto intruders as they leave a business or home, said ABC News.  It can be synced to a panic-button or to any alarm system within a business or home. The solution is both harmless and too small to be seen but will stay on an intruder for weeks, and can linger on clothing for up to six months regardless if it’s been washed. For bags, hats and weapons, the spray will reportedly stay on indefinitely.