Yesterday evening, PBS broadcast an episode of its Nova science program, “Manhunt: The Boston Bombers”, reporting on the role of technology in tracking down those responsible for the Boston Marathon bombings. I had seen a note about the program in our local paper, and was curious to see what sort of program it would be.
I’m glad to say that, on the whole, I thought the reporting was realistic and level-headed. It avoided scare-mongering, and took a fairly pragmatic view of what technology can and cannot do, at least at present. It was organized chronologically, with commentary on forensic technologies interwoven with the narrative.
The first segment dealt with evidence from the explosions themselves. The white smoke that resulted, easily visible in TV accounts, indicated a gunpowder type of explosive, a suggestion reinforced by the relatively small number of shattered windows. One forensic expert, Dr. Van Romero of the New Mexico Institute of Mining and Technology [NM Tech], quickly suspected a home-made bomb built in a pressure cooker. Although devices of this type have been rare in the US, they have been relatively common in other parts of the world. Building a similar bomb, and detonating it on a test range at NM Tech, produced effects very similar to the Boston bombs. A pressure cooker lid was subsequently found on the roof of a building close to one of the explosion sites.
Because the attacks took place very close to the finish line of the Boston Marathon, and because that location on Bolyston Street has a large number of businesses, the authorities were confident that they would have plenty of still and video images to help identify the bombers. After examination of this evidence, they came up with images of two primary suspects, who at that point could not be identified. At first, the police and FBI decided not to release the images to the public; they feared doing so might prompt the suspects to flee, and hoped that facial recognition technology might allow them to be identified. Alas, as I’ve observed before, these techniques work much better — almost like magic — in TV shows like CSI or NCIS than they do in the real world. The images, from security videos, were of low quality, and nearly useless with current recognition technology. Ultimately, the authorities decided to make the images public, hoping that someone would recognize them.
As things turned out, it didn’t matter that much. The two suspects apparently decided to flee, and car-jacked an SUV. The owner of the SUV managed to escape, and raised the alarm. In a subsequent gun battle with police, one suspect died (he was apparently run over by his associate in the SUV); the other was wounded but escaped. He abandoned the SUV a short distance away, and hid in a boat stored in a backyard in Watertown MA. He was subsequently discovered because an alert local citizen noticed blood stains on the boat’s cover; the suspect’s location was pinpointed using infrared cameras mounted on a police helicopter.
As I mentioned earlier, I think the program provided a good and reasonably balanced overview of what these technologies can do, and what they can’t. Magic is still in short supply, but technology can help pull together the relevant evidence.
More work is still being done to improve these techniques. A group at the CyLab Biometrics Center at Carnegie-Mellon University, headed by Prof. Marios Savvides, is working on a new approach to facial recognition from low-quality images. They give their system a data base containing a large number of facial images; each individual has associated images ranging from very high to low resolution. Using information inferred from this data, and guided by human identification of facial “landmarks” (such as the eyebrows, or nose) in the target image, the system attempts to find the most likely matches. The technique is still at a very early stage, but does show some promise. There’s more detail in an article at Ars Technica.
As the NOVA program also pointed out, the growth in and improvement of all this surveillance technology has some potentially troubling implications for personal privacy. Setting up a portion of the infrastructure for a police state is probably not good civic hygiene; but that’s a subject for a future post.