This is second story in a three-part series.

Why did Mika Nishiyama, a former assistant nurse who served 12 years in prison for murdering a male patient in 2003, falsely confess to killing him? That was the greatest mystery about the case, which is due to finally result in an acquittal for Nishiyama later this month.

Without being coerced or threatened, Nishiyama said, “I pulled out the respirator tube from a patient and killed him,” according to investigator records from interrogations prior to her arrest.