The device alerted police officers that the car had been broken into and they tracked down Askale and arrested him. He initially pleaded not guilty in court. But armed with the luminous evidence police and prosecutors were able to prove Askale was behind the crime.

“When Askale stole items from the car, including a laptop, he activated a spray system where he was covered with the substance,” a statement from London’s Metropolitan Police said. “Ultraviolet lights showed that Askale was covered in the spray, proving that he had broken into the car.”