At first glance, communicating a suspect's rights in police interviews appears to be a straightforward task. However, it is more complex than it appears. In particular, for suspects who come from different cultural backgrounds or legal systems and who rely on interpreters in police interviews, ensuring a thorough understanding of their rights and appropriately invoking these rights can be difficult. This paper examines police interviews in which Japanese native-speaker suspects are interviewed by English speaking police officers through interpreters and attempts to identify problems in the processes in which the suspects' rights are communicated through the interpreters. Three issues will be addressed: problematic turn construction; the treatment of a follow-up comprehension check question; and the interference of interpreters' understanding of the rights of suspects. Suggestions will then be given for improvement of caution delivery through interpreting in criminal investigation. The study concerns a number of areas--forensic linguistics, translating and interpreting studies, and conversation analysis--and demonstrates the significance of an interdisciplinary approach to addressing and understanding problems in interpreter-mediated discourse in legal settings.