This chapter examines how an interviewee with borderline intellectual functioning reversed his denial and gave a false confession in investigative interviews conducted by a prosecutor in a murder case in Japan. While the interviewing prosecutor’s varying approaches to questioning are likely to have contributed to the interviewee’s changing statements, the analysis also suggests that the interviewer either ignored or was unaware of the subtle cues of problematic communication, especially the ways in which the interviewee used the phrases wakaranai (I don’t know) and gomennasai (I am sorry), as well as his long silences. It is argued that such miscommunication often arose because of the interlocutors’ mismatch of knowledge schemata. The analysis demonstrates that tension and lack of interactional alignment are likely to have triggered shifts in interactional frames, which gradually led the suspect with a high level of susceptibility to pressure from law enforcement officers to making a false confession. The study suggests that discourse-pragmatic approaches to investigative interviews of vulnerable interviewees can contribute to a better understanding of miscommunication and false confessions, and improvement in interviewing practice. It also brings an insight into the role of the power dynamics operating in the specific context of criminal investigation in Japan.