The conviction of a U.S. minor this week by the Tokyo District Court for the slaying of an Irish exchange student has once again highlighted Japan's lack of a national accreditation system for court interpreters, after the lay judges complained about misinterpretations.

Mistakes were repeatedly observed in the lay judge trial over the killing of Nicola Furlong, 21, ranging from minor interpreting errors and differences in nuance to the complete omission of some of the conversations between prosecutors and the three professional judges and six lay judges.

The lay judges and the defendant's lawyer agreed that these errors ultimately did not affect the verdict, which resulted in an indefinite prison term that will run from five to 10 years because the defendant is a minor. Language experts, however, expressed concern over the fairness of the proceedings.