CLEARWATER - Several pictures of the Boston Marathon bombings are circulating Facebook. One shows an unknown person on the top of a building above the explosions. The caption asks people if they know anything.
It's one of the thousands of images facing FBI agents as they comb through faces of terror and shock to find faces that might look more suspicious.
"If you're looking for that needle in a haystack, face recognition can help you find it," explained Pinellas County Sheriff's Office System Analyst Scott McCallum. "A surveillance image, a bank robbery photo, it could be retail image. It could be any type of face image."
McCallum sifts through images everyday using Face Analysis Comparison Examination System or FACES.
PCSO has the country's largest collaborative facial analysis database, with more than 30 million images contributed by 36 partner agencies. The images are typically inmate or drivers license photos . Investigators conduct about 5,000 searches every month using the system, with matches made every day.
The system is based on a template that maps more than 100 facial features, associating a numeric value for each face, then comparing those numbers.
It takes just five seconds for FACES to return results, but the investigator makes the final match using several options.
"You can overlay the images on themselves so they can align the images appropriately," McCallum said. "Slide these images side by side, or rotate those images as well."
Because facial recognition software is not yet seen as definitive evidence like finger prints, it's not used in court cases, but investigators believe that may soon change. Until then, it will be used it to find suspects, and other evidence used to convict them.
Still, the software speeds up investigations unlike ever before.
"Cases were still solved, but they add a significant amount of value to the investigative process," McCallum said. "To have a mechanism to search that image against other faces and get a robust result is huge. It's paramount to law enforcement."
Copyright 2013 Scripps Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.