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Tokyo police 'relay' security camera method key to solving Shibuya Halloween incident

This photo shows two men on a small truck that has been overturned in Tokyo's Shibuya district on Oct. 28, 2018. (Photo courtesy of Yu Yuki, head of Yu mental clinic, image partially modified)

TOKYO -- Out of the roughly 40,000 people who flooded the Shibuya district here for Halloween celebrations, police were able to identify 15 young men who allegedly overturned a small truck using what they call the "relay" method of security camera investigation.

At 1 a.m. on Oct. 28, Shibuya's center street was in a state of chaos. A dozen or so men surrounded a small truck, lifted it by hand and turned the vehicle on its side. As the 2020 Tokyo Olympics and Paralympic Games approaches, the Tokyo Metropolitan Police Department (MPD) has been stepping up security measures to prevent confusion or accidents caused by large gatherings of people. The case of the truck in Shibuya was given serious consideration -- 43 officers, mostly from the MPD's first investigative unit, which usually handles murders or robberies, joined the case. From there, the survey of the security camera network began.

In Shibuya Ward alone, the MPD has installed roughly 20 street security cameras. Usually, these cameras monitor activity in the busy area and also record the footage. In addition to these police cameras, the unit also gathered video from nearby buildings, shops, train station ticket gates and other privately owned security cameras. Using this information, the MPD was able to trace the movements of the men involved in the incident after it occurred.

White eyeglasses, a backpack, a hat, a baseball jacket -- while running through the footage, police began to pick out characteristics of the men's clothing and other identifying items. For one man, footage of him buying a train ticket from a station machine was discovered, and by enlarging the video of his hands, the amount of money he paid for the ticket was confirmed. From there, police could narrow down the possibilities for the station at which he got off.

Using this method, if a suspect is found to use an electronic transportation card, then the authorities can contact the related railway company and identify the card using information like the time at which it was touched to the sensors at the station ticket gates. The travel history of the card can also be examined. If a suspect uses an automobile, then the police can use the "N system," which automatically read the license plate of a vehicle as it travels, enabling investigators to get a general idea of the path taken.

In the investigation of the truck incident as well, if the station closest to the home of one of the suspects is identified, then police can repeat the process of going to the scene, asking for footage from security cameras managed by local businesses and analyzing the imagery for clues to find the suspect. In places where there are no cameras present, the police work in on-the-ground surveys of the area talking to locals.

By connecting the dots using this investigation method, the police can draw a line between the scene of an incident and a suspect's residence or another location related to them. This is referred to as the "relay method." It is estimated that there are over 5 million security cameras installed across the country, and the MPD even has a video footage analysis expert team at the "Sousa Sien Bunseki Center" (Investigation support analysis center) established in 2009.

On Dec. 5, four of the men whose jumping on top of the truck and other actions were decided to be malicious were arrested on suspicion of violating the Act on Punishment of Physical Violence and Others for group destruction or damage to property. Two were handed a summary order to pay a fine of 100,000 yen, while the indictment of the other two was suspended. The MPD plans to send documents on the other 11 men thought to be involved in the incident to prosecutors.

The men came to Shibuya from Tokyo, as well as the prefectures of Kanagawa to the south, Yamanashi to the west and Gunma to the north, and were between their teens and 30s. Among them were also five foreign nations in Japan for travel or study from countries including Britain, France and Belgium. One foreigner told the MPD that he heard Halloween in Japan was so wild that they would not be arrested no matter how much trouble they caused. The majority of the men appear to have been intoxicated, and those arrested told police they just got caught up in the moment. The investigation made use of a total of 250 cameras.

"Collecting footage from security cameras is a time-consuming investigation method, but it is more reliable for use as evidence than information like witness testimony that relies on human memory," said a senior investigator. "It will only become a more important tool to track down suspects in the future."

(Japanese original by Shota Harumashi, Yoshitaka Yamamoto and Hironori Tsuchie, City News Department)

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