Serial Killer Prompts Japan, and Twitter, to Mull Online Rules

  • Suspect targeted his 9 victims with specific hashtags as bait
  • Twitter’s Dorsey says difficult to oversee all harmful content

The home of suspect Takahiro Shiraishi in Zama, near Tokyo. 

Photographer: Kyodo News via Getty Images

A Japanese serial killer’s alleged use of Twitter to lure victims to his apartment has prompted the government and the social-media platform to look at how the tool is regulated in the country.

Police arrested a 27-year-old man after saying that they found nine dismembered corpses at his home in Zama, about 40 kilometers (25 miles) southwest of Tokyo. He lured his victims using hashtags aimed at people tweeting about wanting to commit suicide. Takahiro Shiraishi has admitted killing all nine people -- including a girl as young as 15, according to local media.

Suspect Takahiro Shiraishi

Photographer: The Asahi Shimbun via Getty Images

Chief Cabinet Secretary Yoshihide Suga said last week the government will convene a special committee to create a plan to prevent recurrences by year-end. The government last year revised an anti-stalking law to include social media posts after a young woman was attacked by a knife-wielding assailant who had threatened her on Twitter.

Twitter Inc. Chief Executive Officer Jack Dorsey commented on the case on a visit to Tokyo this week.

"It’s very unfortunate, it’s extremely sad," Dorsey said Wednesday. He addressed the need to ensure the tool was used in "positive and healthy ways," but noted the difficulties in completely eradicating all harmful tweets related to suicide.

A spokeswoman for Twitter’s Japan operation said the company frequently communicates with the police and other agencies, and plans to continue the discussion on safety. Earlier this month, the company clarified guidelines on what posts are permissible under Twitter rules, specifying that any posts that encourage or promote suicide and self-harm are against company policy.

Kaori Hayashi, professor of media and journalism at the University of Tokyo, said Japan has long neglected the debate on how freedom of expression ties in with social media.

While the government may ask companies like Twitter and Facebook Inc. to impose some restrictions on language, Hayashi said it’s unrealistic to directly regulate them.

"You can’t just turn off the faucet on speech," she said.

— With assistance by Isabel Reynolds, and Pavel Alpeyev

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