Соответствующая норма
Practice Relating to Rule 100. Fair Trial Guarantees
Section H. Assistance of an interpreter
Japan’s Code of Criminal Procedure (1948), as amended in 2006, states:
Article 175
When the court has a person who is not proficient in the national language make a statement, it shall have an interpreter interpret it.
Article 176
When the court has a person who is unable to hear or speak make a statement, it may have an interpreter interpret it. 
Japan, Code of Criminal Procedure, 1948, as amended in 2006, Articles 175 and 176.