Japan
Criminal investigations in Japan
How investigation and charging are divided: the police act as judicial police officials investigating offences, public prosecutors may also investigate, and it is the prosecutor who institutes the prosecution.
Facts on this page were checked against their sources on .
Criminal investigation in Japan is carried out mainly by the police, who act as judicial police officials investigating offences under the Code of Criminal Procedure. Because policing is prefectural, the day-to-day investigative work is done by the prefectural police within their areas, within the national framework of the Code.
Public prosecutors are not confined to the courtroom. Under the Code of Criminal Procedure a public prosecutor may, when necessary, investigate an offence himself, and it is the public prosecutor who institutes the prosecution. So investigation is shared — principally the police, with the prosecutor able to investigate — while the decision to charge rests with the prosecutor alone.
The same idea, explained generally
- What is a criminal investigation?
A criminal investigation is a legally authorised process for establishing whether an offence occurred and gathering evidence that can be tested in court. This guide explains its structure, safeguards, and known failure modes.
- What is due process?
Due process is the requirement that the state follow fair, established procedures before it takes action against a person. This guide explains what it typically includes and how it differs between systems.
Sources
Sources
Code of Criminal Procedure (刑事訴訟法), English translation
Ministry of Justice (Japanese Law Translation database) · Legislation · 1948 · link verified 2026-07-25
Cited from the official Japanese Law Translation database (reference only; original Japanese text has legal effect). Supports, at the structural level: that police officials act as judicial police officials investigating offences (Article 189); that public prosecutors may themselves investigate offences (Article 191); and that prosecution is instituted by a public prosecutor (Article 247), who holds the discretion whether to prosecute. Supports the allocation of investigative and charging responsibility; the English is not authoritative and no operational detail is drawn from it. WAVE 22 ADDITION. Read again from the same Japanese Law Translation page, this time from the database's own XML export of the Code (s23Aa001310201en2.0_h18A36.xml), fetched with the law page as referrer. TEMPORAL LIMITATION, stated because it is load-bearing for this wave: the version identifier indicates a translation reflecting amendments to 2006, so it MAY LAG later amendments, and only structural propositions present in that version are drawn from it. Supports Art. 197(1): with regard to investigation, “such examination as is necessary to achieve its objective may be conducted; provided, however, that compulsory dispositions shall not be applied unless special provisions have been established in this Code.” Supports Art. 218(1), that a public prosecutor, a public prosecutor's assistant officer or a judicial police official may, if necessary for investigation of an offense, conduct search, seizure or inspection UPON A WARRANT ISSUED BY A JUDGE, and Art. 218(3), that the warrant is issued upon their request. Supports Art. 219(1), that the warrant shall contain the name of the suspect or accused, the charged offense, THE ARTICLES TO BE SEIZED or the place, body or articles to be searched, the place or articles to be inspected, the valid period, and a statement that the search, seizure or inspection shall not be commenced after the lapse of that period and that the warrant shall then be returned to the court. Supports Art. 222-2 in full: “Compulsory measures for the interception of electronic communications without the consent of either party shall be executed based upon other acts.” Cited for three propositions: that a national code can state as a general rule that a compulsory measure requires a specific statutory provision; that the warrant instrument itself distinguishes what may be seized from what may be searched; and that a system may place the interception power OUTSIDE its general procedure code. The Act to which Art. 222-2 refers was NOT read, and this record supports no claim about its content. The English is a reference translation and the Japanese text has legal effect.
National Police Agency (NPA), Japan · Government publication · 2020 · link verified 2026-07-25
The NPA's own English overview; figures and wording extracted directly from the report PDF. Supports: that the National Public Safety Commission (NPSC) and the National Police Agency (NPA) constitute the national police organisation and the NPSC supervises the NPA; that the Police Act empowers the national government to establish a central police organisation 'to control and supervise prefectural police forces on matters of national concern'; that the NPSC 'draws up basic policies and regulations, coordinates police administration on matters of national concern and sets general standards'; that each prefecture has 'the authority to carry out police duties'; that Regional Police Bureaus are subordinate to the NPA; that police boxes (Koban) and residential police boxes (Chuzaisho) are subordinate units of police stations; that the Tokyo Metropolitan Police Department is the prefectural police of Tokyo; and that 'the Prime Minister is not empowered to exercise direct command or control over the Commission'. CRUCIALLY, it supports national COORDINATION, STANDARDS and SUPERVISION ON MATTERS OF NATIONAL CONCERN, with operational policing carried out by the prefectures — NOT a single nationally commanded operational police force. Does not support operational detail.