Before fugitive Aum Supreme Truth cultist Makoto Hirata, 46, turned himself in at the Marunouchi police station in Tokyo’s Chiyoda Ward on New Year’s Eve, it was determined he had passed through JR Shinagawa station.

How do we know this? Because his image was eventually picked up and recorded by one of the security cameras mounted in the station.

But still, points out web newspaper J-Cast News, Shinagawa is a huge station through which an average of over 320,000 people a day pass through. So how could Hirata be picked out from the other 319,999 or so rail commuters that day?

Well, there are two possibilities. Either the cameras at the station are linked to a computerized “face recognition system” or Hirata was spotted by a human tasked with monitoring the passers-by. At face value, the latter appears unlikely as a dependable means of capturing a single face in the crowd.

The newspapers that reported the spotting of Hirata in Shinagawa did not offer an answer to the above question, using vague terms such as “the video image of a man who appeared to be Makoto Hirata.” The Tokyo Metropolitan Police would only remark, “If a photo with a frontal view of someone’s face were available, and if it were possible to search out a face (from a database) based on what the camera in the station picked up, then this might be possible.”

Electronics manufacturer NEC, which introduced a face recognition system from 2002, told J-Cast News that “There are various conditions involved.” During tests conducted in the U.S. in 2010, NEC’s recognition system was rated the “world’s best.”

Face recognition, in a nutshell, operates by converting a frontal view of the face into a simulated three-dimensional image, creating a pattern that is unique as are fingerprints. The technology is already so well advanced that it is utilized by some smartphones as a “lock” to prevent misuse by anyone except the phone’s owner. NEC technology (fingerprint and facial recognition) is utilized at airports, including at Narita and by Hong Kong’s immigration department, to search for those on international wanted lists.

Facial recognition, which is said to be “96% to 97% accurate,” is seen as an effective complement to fingerprint checking. It cannot be tricked by attempts at disguise such as wearing eyeglasses or growing a beard. However, accuracy depends to a large extent on the availability of the camera’s capturing a frontal image; if only the profile is captured by the camera, accuracy may drop to 80%—in some cases as low as 50%.

So law enforcement agencies and others are reminded of these limitations, with the disclaimer that while a facial recognition system may be able to pick out a person with physical similarities to a crime suspect, final verification “ultimately depends on the human eye.”

Likewise, the identification of Hirata from the videos in Shinagawa station is believed to have been the result of painstaking efforts on the part of investigators rather than hi-tech gadgetry.

Nevertheless, authorities are viewing the new technology with increasing confidence. According to a source at Minato Ward-based Security Design-sha, a supplier of such technology, 3D facial recognition has reached the stage where it “can even make distinctions between identical twins.”

One way the technology is being refined to achieve greater accuracy is through image enlargement technology. Just last month, NEC announced “super resolution technology” that could enlarge captured images fourfold with excellent clarity.

Currently according to the Ministry of Land, Infrastructure, Transport and Tourism, 56,000 security cameras had been installed in rail and subway stations nationwide. Metropolitan Tokyo bolstered its budget, adding 2,975 new cameras between 2004 and 2010.

However, objections have been raised that the use of such cameras constitute a violation of citizens’ privacy. An association of attorneys in Fukuoka has issued a protest, questioning security camera effectiveness and maintaining there is no clear correlation between camera installation and crime prevention.

“The whittling away of privacy is having major side effects,” the Fukuoka group asserts. “As far as the ‘effectiveness’ of security cameras, matters should be decided while calmly examining the numbers, without any preconceived opinions.”