Admissibility of the Evidence Obtained by the Foreign Officials : Jurisprudence of the United States Courts and Its Applicability in Japan

Abstract

In today's age of globalization, it is not uncommon for evidence of a crime to be located overseas. Japanese investigators or prosecutors who encounter this circumstance must ask foreign governments to collect the evidence and send it to Japan. Yet not uncommonly, foreign authorities obtain evidence by means or procedures that would be unlawful under Japanese law. Under what standard or framework should the admissibility of that kind of evidence be decided in Japanese courts? The exclusion of evidence on the grounds of trivial procedural differences would thwart international collaboration in criminal investigations, to be sure. But should such evidence always be admitted? Are there exceptional cases where such evidence must be excluded? This note will first review the decisions in the Japanese courts and conclude that no concrete standard or framework has yet been formed to decide the admissibility of this kind of evidence. Second, this note will examine how courts in the United States address this issue. This examination will turn up two exceptional cases where evidence collected by foreign authorities must be excluded: one where the "joint venture" doctrine applies and the other where the conduct of foreign authorities "shocks the conscience." Finally, this note will examine the rationale of excluding evidence in those exceptional cases and argue that there is leeway for bringing those exceptions into Japanese jurisprudence.