Kashouko (工藤加寿子), a single mother who was last seen at the time, was a primary suspect. However, due to insufficient evidence, the case could not be closed. After that, a fire broke out in Kashouko's house, and her husband was burned to death. The remains of the children were found in the burnt house. Police have repeatedly investigated Kashouko but have been unable to convict her. In November 1998, 14th years after Shiromaru-kun's disappearance, the development of DNA technology allowed the police to confirm that the child's remains found belonged to Shiromaru-Kun. Police ruled a murder. However, it is only a month away from the time limit for the case's prosecution(then 15 years indictment period). Jia Shouzi rejected the prosecution's nearly 400 questions during the lawsuit with "I don't want to answer." She effectively applied the Miranda rights (Miranda warning) so that the trial could not convict it. Instead, she received compensation for her imprisonment and lawsuits.
The Shiromaru-Kun incident caused a stir in Japan because the public believed that Kashouko was a criminal but could not convict her. The offender was successfully cleared by effectively applying the law of silence and the validity of the lawsuit.
Japan revised Criminal Procedure Law, promulgated and implemented on April 27, 2010, abolished the statute of limitations for "criminal homicide" and changed it to indefinite.
Miranda warning: " You have the right to remain silent. Anything you say can be used against you in court. You have the right to talk to a lawyer for advice before we ask you any questions. You have the right to have a lawyer with you during questioning. If you cannot afford a lawyer, one will be appointed for you before any questioning if you wish. If you decide to answer questions now without a lawyer present, you have the right to stop answering at any time."