Friday, January 10, 2014
Kanagawa Police recapture escaped suspect using phone location data
Posted by SBS
On January 7, Sugimoto Yuta bolted from a sixth floor, unsecured interrogation room at a Kawasaki police station while under arrest for suspicion of robbery and gang rape. He was unguarded and meeting with a lawyer at the time. He was recaptured 46 hours later in a Yokohama Park along the Tokaido Main Line, approximately 20 kilometers from the police station.
Sugimoto was spotted on a security camera getting in two a car with two of his friends. The police later determined that Sugimoto had borrowed a cell phone from one of the two. The police then tracked that phone with location data provided from the carrier to the vicinity of Izumi and Seya Wards in Yokohama, where they eventually located Sugimoto in a wooded park.
The mobile carrier and phone type was not reported. The phone was referred to as a keitai denwa (携帯電話) which could technically be used to refer to either a smartphone or a feature phone, but is generally these days used to describe feature phones. Based on the imprecise location data, it would seem that the police had only cell tower triangulation available. (Alternatively, they could have tracked the phone precisely to a number of locations within those two wards.)
Japanese mobile carriers do collect precise location data on customers using GPS. You may recall the animations that were produced by from NTT Docomo data of the exodus, primarily on foot, of people from Tokyo following the 3/11 Earthquake. Unfortunately the videos are no longer publicly available.
You also may recall that the Tokyo Metropolitan Police recently began pushing for ID verification for data-only SIM cards that are provided by MVNOs. These prepaid data SIMs have sufficient bandwith to support VoIP and SIP clients, so they can be used for voice communications. This recent case will likely be used as an example of why ID registration requirements should be expanded to data SIMs, without which, the police would be unable to track a person based on their mobile device.