Thief convicted after being caught green-handed (and faced)

Yafet Askale, 28, was convicted of stealing from a car after he was sprayed with SmartWater. Ultraviolet lights showed Askale had been covered with the substance. Metropolitan Police

LONDON -- A chemical mist which turns perpetrators florescent green is being used to target thieves in Britain.

Officers have started fitting SmartWater technology to security systems in cars and houses in the U.K.'s capital.

When someone tries to break in, they are sprayed with the odorless substance which is only visible under ultraviolet light and cannot be washed off. 

The arm of Yafet Askale, who was convicted of stealing from a car after he was sprayed with the odorless chemical mist. Metropolitan Police

Crooks have no idea they have been tagged -- until it is too late.

The dramatic effect can be seen in these photos of Yafet Askale, a 28-year-old who stole a laptop from a "trap car" in the Brent area of London which police had fitted to spray the mist, which is known as SmartWaterCSI in the U.S.

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."

Askale appeared in court on Friday and was sentenced to 49 hours of community service and a fine of £400 (about $650).

The technology can also be used on the front doors and windows of homes.