Catching Terrorists Carrying Bombs Still a Tough Problem to Solve

When police in Watertown, Mass., honed in on Boston Marathon bombing suspect Dzhokhar Tsarnaev hiding in a boat stored in a backyard in April, they had several tools familiar to service members who fought in the Iraq and Afghan wars at their disposal.

A Star Safire High Definition sensor manufactured by FLIR Systems mounted on a helicopter was able to provide authorities with an image of Tsarnaev under a tarp. An iRobot Packbot was then sent into for reconnaissance before police surrounded the boat and apprehended the suspect.

Missing from the equation is a technology that may have prevented the bombing — stand-off detection for person-borne improvised explosive devices.

The problem is that there is nothing commercially available for police departments or other security entities that can scan a crowd, pick up the signatures of hidden explosives and alert officials to the presence of a bomb, said Jimmie Oxley, co-director of the Department of Homeland Security’s center of excellence for explosives detection, mitigation and response at the University of Rhode Island.

There are companies that are working on the problem, she said. Suicide bombers are a particular concern because by the time they reach a checkpoint, it is too late. They can still claim many victims.

There are sensors that use various methods to detect smudges of explosives on clothing from distances, or a plume of chemical vapors emitting from a backpack, such as those allegedly carried by the Tsarnaev brothers.

“The problem is that each of those techniques has issues,” Oxley said.

One example is Raman-based spectroscopy systems, which use lasers to identify the chemical composition of items from a distance. They have performed well in field tests, but it is not safe for eyes. That is unacceptable in applications where it scans crowds for telltale signs of explosives, she said.

“You need a system where you can reach at a distance, and get feedback back, and you’re going to want to scan a crowd,” she said.

There are systems that use infrared, terahertz and visible light. Radar systems search for anomalies under clothes, which may or may not be explosives. It can spot guns or bombs because their heat signature is different from skin.

Another problem is the numerous kinds of explosives, she said.

“There are so many different kinds of explosives. If you were just detecting chemical X, you could probably do a pretty good job of detecting it, but you need to detect all other 26 letters of the alphabet,” she said.

Small companies are working on the problem, but making inroads with the Transportation Security Administration — one of the largest customers for explosive detection systems — is key, Oxley said.

“If they don’t sell it to the TSA market, they don’t get enough money to drive their systems toward further development,” she added.

They may need a secondary source to avoid the so-called “valley of death,” where ideas and prototypes for technologies die when they can’t find customers. She knows of one company that found some success applying its bomb-seeking system to finding leaks in gas lines.

Oxley remains hopeful that law enforcement will one day be able to scan a crowd with a sensor and pinpoint bombers.

“I don’t think it is an impossible goal, but I think we have to take it a little at a time,” she said.

Topics: Bomb and Warhead, Improvised Explosive Devices, Homeland Security, Disaster Response, Science and Technology