Recently, a Subway sandwich shop in Knoxville, Tenn. equipped their store’s entrance with SelectaDNA, an invisible spray comprised of synthetic DNA, UV adhesive, and hundreds of microdots. When triggered, the spray covers burglars in the solution; police can then use UV lights to detect the spray and read its unique DNA code. A similar solution called SmartWater leaves burglars with a semi-permanent green glow, only visible under UV light, that takes weeks to wash off the skin and is almost impossible to remove from clothing. The police need just a tiny bit of the sample for decryption in order to connect a suspect with the crime scene.

As successful as SmartWater and SelectaDNA have been in deterring would-be thieves—even stickers warning about their presence have helped cut down on crime—they don't do anything to stop burglars in their tracks. Over the past century, there have been plenty of attempts to create thief-trapping devices, but so far, the results have been pretty mixed.

1. Trap Door

According to the “New Miscellaneous Inventions” section of an 1877 issue of Scientific American, this trap, patented by W.E. Wharton in 1877, consisted of tilting sections on the floor in front of a store or bank’s counter that, when triggered, “precipitate the thief or burglar into the cellar or apartment below,” placing him in “a place of secure confinement without incurring the danger of personal encounter and injury.”

2. Sleeping Gas

This burglar trap, invented in 1935 by a policeman in Budapest, favored sedation over entrapment—by knocking the robber out cold. The New York Times article “Trap for Cracksmen” explained the workings of the contraption: “A special gas compressed in a container is fitted inside the safe in such a manner that a burglar’s tool piercing the safe releases the gas also. A few breaths of the escaping fumes lulls the burglar to sleep for several hours and makes his arrest easy.” 

3. Pickles

Laymen hoping to thwart a criminal's plan have often resorted to handmade booby traps and spying devices. A 1957 New York Times piece, “Burglar Again Outwits Pickle Trap in Yonkers,” describes a store owner who rigged a trap “with two 5-gallon glass jars, each filled with pickles and brine. Every night at closing, he … carefully set the open jars on a trap door leading from the basement, in the hope that when an intruder opened the door he would be surprised by pickles.” As the headline implies, it didn't work.

4. A Descending Box

In 2001, Kuo Cheng Hsieh, the head of a security company in Taiwan, received a patent for his own burglar-trap invention. As a former commander of a frogman unit, Hsieh had used nets to snare swimming Chinese spies. This experience, along with his knowledge of ancient hunting nets, influenced his creation of a bank security system that could drop a net on an escaping thief. According to Hsieh's patent,

The device looks like a storing box and is installed above the entrance of the business. When a robbery takes place and the system is activated, an infrared detecting device determines if a robber is in a zone beneath the storing box. A net, a curtain, and a plurality of barriers will drop down immediately and simultaneously. After a lifting motor is activated, the system traps the robber and suspends him above the floor.

In 2007, he was awarded an Ig Nobel Economics Prize for his invention.