Japanese police have arrested a man whom they say raped about 100 women under the guise of participating in a sleep study.

Starting in 2012, Hideyuki Noguchi, 54, ran ads in newspapers looking for women willing to join a sleeping experiment where all he required was their permission for him to take their blood pressure. Instead Noguchi sexually assaulted the women after they were drugged, then he recorded the attacks and sold the clips to porn websites. He made nearly $100,000 from his "work," according to CNN's Will Ripley. Police were alerted to Noguchi's exploits when one victim say herself in a video.

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Ripley says Noguchi will likely spend a good amount of time behind bars because Japan has a 99 percent conviction rate.