The Tokyo High Court on Wednesday nullified the confession of a Filipino woman accused of killing her live-in boyfriend in 1997, saying it was obtained through illegal police action, but nevertheless upheld her prison sentence for murder.

The court upheld the eight-year sentence handed down to Manalili Villanueva Rosal, 30, by the Chiba District Court in 2000 for the fatal stabbing of Hideyuki Takahashi, 30, with a kitchen knife at their apartment in Matsudo, Chiba Prefecture, in November 1997.

The high court said Wednesday that police confined and questioned Rosal without a warrant in locations that include a hotel room and a police dormitory until, after 10 days, she confessed. After she was turned over to prosecutors, she denied committing the crime.