Digital Eyes on Boston Marathon Require Human Analysis

U.S. and Massachusetts authorities investigating the Boston Marathon bombings made pleas throughout the day: Send us your pictures.

“It’s our intention to go through every frame of every video we have,” Boston Police Commissioner Ed Davis said at a press conference yesterday.

Yet the modern treasure trove of digital evidence -- from government and business cameras and the smart phones of marathon spectators gathered April 15 in Copley Square -- can’t be unlocked without old-fashioned police work, said Mark Clifton, a vice president of SRI International, a technology development company based in Menlo Park, California.

“Unfortunately it’s a very manual process,” Clifton said in an interview. “There’s no program or search algorithm that’s as good as people.”

A few crucial details could help the Federal Bureau of Investigation and other police officials as they begin what could be a weeks-long process of scouring the footage.

Yesterday, a Boston television station released photos taken before the explosion showing a bag lying next to a mailbox and against a race-route barricade. A second picture, blurred by WHDH-TV because of its graphic content, suggested the blast was centered where the bag had been placed. The viewer who took the pictures said an hour or more may have elapsed between the two images, according to WHDH.

Pressure Cookers

Authorities said evidence suggests the bombs were built inside metal pressure cookers, perhaps concealed in a black backpack or duffel bag. And police swept the finish-line area for explosives the morning of the race and about an hour before elite runners began crossing at about noon, Davis said. That leaves about a four-hour window before two explosions at 2:50 p.m. killed three people and injured scores of others.

“The problem a bomber has is he wants to get into a populated area without getting caught, but he can’t get there too early because it’ll get found and he can’t get there too late because the activity will be over,” said Jerry Richards, former chief of the FBI’s special photographic unit. “It’s kind of a conundrum, fortunately for us.”

Police will want images from any camera “that was pointed at” the location of the bomb blasts, Richards said in an interview.

Photo Triage

“They will be inundated with video and it’ll be like a hospital triage,” said Richards, who owns Richards’ Forensic Services, based in Laurel, Maryland. “They will sift out the good from the bad from the ugly.”

Authorities began yesterday by asking anyone with original video or images from the finish line to send the information to the Boston headquarters website. That e-mail address was mentioned hundreds of times on social media sites including Twitter and Facebook.

On top of smart phones, Richards estimated there are “hundreds” of surveillance cameras in the area where the bombs exploded.

At an afternoon briefing, Richard DesLauriers, special agent in charge of the FBI’s Boston office, said investigators have seen a “tremendous outpouring” in response to their call for videos. Experts from the FBI’s laboratory in Quantico, Virginia were on their way to Boston to assist in analysis that had already begun, he said.

London Experience

Obtaining the footage will be “the easy part,” said Brian Adamson, who spent 10 years as an evidential imaging officer with the Metropolitan Police in London. The U.K. is known for its thick web of surveillance cameras; studies have pegged the number at anywhere from 2 million to 4 million.

With videos in hand, Adamson said in an interview, investigators begin the painstaking process of creating a reverse time line from the explosion to the point where the bombs were put in place.

“You start from the explosion and literally walk backward, physically looking up and down the road for all of the cameras that you can see,” he said.

That’s how British authorities found four bombers after the July 7, 2005, London subway explosions that left 56 people -- including the perpetrators -- dead.

Video Fatigue

In the days after the subway bombings, 50 or more investigators would sit in police offices converted into viewing rooms looking at video after video, Adamson said.

“When you don’t know what you’re looking for, you just watch for something that doesn’t seem right and then research that,” he said.

This will mean hours of tedious work, he said.

There is no software reminiscent of the tools seen on television crime programs, Clifton said.

“If they have an idea of what they’re looking for and maybe have a snapshot of a person or an object, they can run some programs or facial-recognition software that will help, but they’re not that reliable,” Clifton said. Coming up with an algorithm that searches as well as a trained police officer is “the holy grail” the surveillance industry is pursuing.

To stay focused during the manual search, Adamson said the investigators would be wise to take breaks every hour and frequently switch the footage they’re reviewing.

‘Same Song’

“A change for your eyes and your brain is important,” he said. “Otherwise it’s like listening to the same song over and over -- you just begin tuning out parts of it.”

Grant Fredericks, who owns Forensic Video Solutions in Spokane, Washington and is a former coordinator of the Vancouver Police Department’s forensic video unit in Canada, said there will be plenty of material for investigators to work with.

“I can guarantee this: There is a lot of video of the person or persons who planted those bombs,” Fredericks said in a phone interview. “Anyone who was down and around the sports event in Boston likely would have been captured on hundreds of cameras.”

The bomber or bombers “entered a gauntlet of evidence collection systems,” said Fredericks, who works with the Law Enforcement and Emergency Services Video Association (LEVA) lab, hosted at the University of Indianapolis.

“More than DNA, more than fingerprints, more than eyewitness testimony, video sources are available to law enforcement at an unprecedented rate today,” Fredericks said. At the marathon, “everyone was collecting evidence for the police. They didn’t know it at the time, but everybody has evidence.”

Vancouver Riot

Fredericks and a team of LEVA investigators helped untangle crimes from the June, 15, 2011, riots in Vancouver when the Canucks hockey team lost to the Boston Bruins in the Stanley Cup Finals. The riot caused more than $3.4 million in damage, police said.

He said more than 50 investigators from around the world processed and analyzed more than 5,000 hours of video. The team identified 15,000 criminal acts and tagged perpetrators with unique codes.

If authorities in Boston do identify a suspect -- be it through the videos or through other methods of investigation -- the footage will continue to be useful in building a court case, said Tom Owen, an audio and video expert at Owen Forensic Services LLC, a digital processing lab in Colonia, New Jersey.

Yet an influx of videos from unidentified bystanders could end present legal challenges for prosecutors, said Owen.

Video may not be admitted as evidence in court if officials don’t know the time, date and location where it was taken, plus the contact information of the person who sent the information, he said.

“Those questions have to be answered in order for it to be admitted to a court of law,” Owen said. “To a certain extent, they can track it on the Internet, but not always. It’s not like it is in the movies.”

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