"Computer Forensics" is defined as "the recovery of deleted computer-based information and the science of examining and piecing back together the who, what, when, where, and how of computer-related conduct." According to the other definition, "Computer forensics deals with the preservation, identification, extraction, and documentation of computer evidence."¹ More and more venture companies and risk consultant company try to apply this computer forensics into the business in US. Seminars to advertise their forensic business are held even in Japan these days. Forensic services includes (1) expert testimony and reporting services, (2) research and recreate critical events, (3) custom forensic analysis, (4) legal and technical consulting. And more broadly, it involves the identifying "hackers" who try to intrude into the systems of ISP and /or deny the service of them.

Many books of which titles are such as "Computer forensics" are published. NPA published their concern about the "computer forensics" in their WebPages. In the nature, "computer forensics" has close relationships with legal system. The purpose of this article is to make a comparative study of influences over the forensic approach by the differences of the legal systems.