The chief of Shiga Prefectural Police department apologized Thursday to a former assistant nurse who was acquitted of murdering a patient in a retrial after serving her prison term.

The apology from the Shiga police chief, Hisaaki Ikeuchi, came after a local court ruled that the prefectural police's investigation into the 45-year-old former assistant nurse, Mika Nishiyama, was illegal.

"We sincerely apologize for the indescribable stress and burden we have caused for more than 21 years since the arrest to today," Ikeuchi said, bowing to Nishiyama and her parents at a prefectural government office in Hikone.

The police arrested Nishiyama in July 2004 on suspicion of murdering a male patient at a hospital in Shiga in 2003, based on her confession during the police investigation. She pleaded not guilty during her trial, but was sentenced to 12 years in prison.

A high court granted her a retrial after she finished her prison term, recognizing that there were suspicions over the credibility of her confession. Her acquittal was finalized in April 2020.

In July this year, Otsu District Court ordered the Shiga Prefectural Government to pay about ¥31 million in damages to Nishiyama, finding the police investigation illegal. The order became final.

But the court at the same time rejected Nishiyama's claim for damages from the central government, saying that her indictment by public prosecutors was reasonable to a certain degree. Nishiyama has appealed against the ruling.