CURRENT SITUATION OF CORRUPTION INVESTIGATION IN
THE JAPANESE PUBLIC PROSECUTORS’ OFFICE—CHALLENGES AND MEASURES TO OVERCOME THEM—
Shinichiro Iwashita*

I.

INTRODUCTION

A. Authorities which Investigate Corruption Cases
Although Japan has no specialized commission or agency which is responsible forinvestigating corruption cases, there are two authorities that have responsibility forinvestigating them: police officials 1 and public prosecutors 2. If a police official launches acriminal investigation, the official must refer the case to public prosecutors along with the
documents and evidence. Upon receiving the case, the public prosecutor begins his or her
own investigation. The public prosecutor can request the police to conduct further
investigation and to collect more evidence crucial to proving the offender’s guilt; theprosecutor can also directly interrogate suspects and interview key witnesses to determine
whether to indict the suspect or not. Moreover, the public prosecutor is able to launch a
criminal investigation based on the prosecution’s discretionary investigative power, without
having to rely on any assistance from police officials. Thus, public prosecutors have two ways
to investigate corruption cases: independently or through collaboration with police officials.
Currently, most corruption cases (over 99％) are initially investigated by the police, and avery small number of cases (less than 1％) are investigated by public prosecutors independently.
The cases public prosecutors investigate independently tend to be limited to the major corruption
cases involving politicians, high-ranking officers, and complicated economic crimes.
B. The Special Investigation Department (SID) for Corruption Cases in the Public
Prosecutors’ Office
In large public prosecutors’ offices, public prosecutors are divided into several departments
and share the work. The investigative department is in charge of investigating and deciding
whether or not to indict suspects referred from the police, and the trial department is in charge ofconducting trials (proving guilt of the accused). Moreover there is the Special Investigation
Department (SID), which investigates major corruption cases and complicated economic cases.
Public prosecutors in this department investigate cases independently (they do not deal with thecases initially investigated by the police; those cases are dealt with by the prosecutors in theinvestigating departments). In Japan, the district public prosecutors’ offices in Tokyo, Osaka andNagoya have SIDs, and the SID of the Tokyo District Public Prosecutors’ Office is the biggest.3*

UNAFEI Professor and Public Prosecutor in Japan.
The Criminal Procedure Code (CPC) stipulates police officials as the primary investigative authorities and obligatesthem to investigate any crime; it says police officials shall investigate criminal cases when they deem that an offense
was committed.
2
The CPC also gives the power of investigating all criminal cases to public prosecutors, but it leaves that power to theprosecutor’s discretion; it says that public prosecutor may investigate criminal cases when he/she deems it necessary.
3
The SID of the Tokyo District Public Prosecutors’ Office has around 30 public prosecutors and around 80 assistantinvestigators.
1- 76 -

These three SIDs, especially the SID of the Tokyo District Public Prosecutors’ Office, play a greatrole in the investigation of corruption cases committed by politicians and high-ranking officers.
II. INVESTIGATIVE METHODS FOR CORRUPTION CASES
Corruption cases, typically bribery, are ordinarily committed in secret among a very limited
number of parties. No individual victims exist and neutral witnesses are few. In addition,
fingerprints, footprints and DNA are rarely discovered at the scenes of corruption crimes. Thismeans that corruption cases are some of the most difficult criminal cases for investigative
authorities to obtain effective evidence. Although it can be said that special investigativetechniques, such as electronic surveillance, wiretapping, eavesdropping, undercover/sting
operations, and plea bargaining or immunity, are very effective, Japan has not adopted such special
investigative methods for corruption cases. With such severe limitations on investigation, thefactors mentioned below are crucial to successful prosecution of corruption cases.
A. Intensive Collection and Analysis of Objective Evidence
1. Tracing the Flow of Funds
In the investigation of corruption cases, identifying and proving the flow of illicit funds is
crucial. For example, in bribery cases, tracing the flow of money—namely from the source of thebribe to the receipt of the bribe as well as the concealment or use of the bribe by the bribe-taker—isindispensable to prove the facts of the case objectively. Also, tracing the flow of money enables
investigators to confiscate the bribe as criminal proceeds from the offender.
However, this is very difficult for investigators to do, because the flow of illicit funds isalways concealed and the criminal proceeds are often laundered by moving the money in legaltransactions from bank to bank, which hinders investigators from tracing money.
To overcome such challenges, thorough and careful financial investigation is very important.
In Japan, the SIDs have many trained assistant investigators who assist prosecutors, and they aretrained to get bank records quickly4 and also know where and what kind of records are kept in eachfinancial institution. All transaction information written in the bank records gathered is integrated
into a “transaction table” (which is one tabular form), and investigators use the table to trace andidentify the flows of money connected with bribery. Finally, investigators find the secret source ofthe bribe or discover pseudonymous bank accounts which are likely to be highly connected withbribery.
2.

Search and Seizure
Needless to say, thorough search and seizure is fundamental to achieve thorough gathering ofobjective evidence. The following are the key factors to succeed in search and seizure.
(i) Simultaneous seizure
In usual cases, it is necessary to execute search and seizure at several places to collect related
evidence, such as the houses and offices of bribe-giver and bribe-taker, and so forth. In such cases,
simultaneous execution of search and seizure is the best practice, because the more time it takes,
the more the risk of concealment and destruction of important evidence increases. To realize
effective simultaneous seizure, it is crucial for investigators to make a plan of execution carefully. 5
4

In Japan, it is not necessary to obtain a court order to request bank records from financial institutions.
For example, where and how many places should be searched, what kind of evidence should be seized at each place,
how many public prosecutors and assistant investigators are necessary to complete the search and seizure, and so on.

5- 77 -

(ii) Arranging an effective search team led by a good team leader
In order to effectively execute a search at many sites at the same time, it is important toestablish a good search team that can communicate well. Also, a good leader should be assigned
who can give prompt and appropriate direction to the team.
(iii) Gathering efficient personnel for the search teamSometimes, there may not be enough investigators available to conduct the search and seizure
because there are so many places necessary to search. To cope with such situations, it is effective
to build a system which enables cooperation with investigators from other divisions in order toassist with the search and seizure. In Japanese public prosecutors’ offices, when the SIDs needfurther prosecutors and assistant investigators to conduct simultaneous searches and seizures, many
public prosecutors and assistant investigators in other departments or other district publicprosecutors are transferred to the SIDs for limited periods to enable the SIDs to achieve
simultaneous searches and seizures under the direction of the Chief Prosecutor.
(iv) Sharing information within the team
It is indispensable for the search team to share necessary information 6 among the teammembers. In the SIDs, advance briefing is usually held before the search. In most cases, the publicprosecutor in charge firstly explains the case and what material evidence should be seized, andafter that each search team has its own meeting led by the team leader in preparation for theirsearch.
(v) Analysis of seized evidence
Analysis of the seized evidence must begin immediately after finishing the search and seizure.
Thorough and swift analysis of seized evidence is fundamental to a successful investigation. To
analyse evidence swiftly and efficiently, it must be done systematically. Therefore, establishingspecial units for analysing evidence is very effective. In the SIDs, after search and seizure,prosecutors and assistant investigators are divided into several groups and are assigned items of
seized evidence to analyse by the prosecutor in charge. Such assignment is usually based on thelocation of the evidence or an issue or person to which evidence is supposed to have a connection.
It is also important to share the results of the analysis of evidence. The SIDs always makea database which is called “The list of articles of evidence”. The information of evidence isconcentrated into this database and each public prosecutor and assistant investigator inputs
information as the result of analysis of evidence, such as the number, name and quantity ofthe evidence, where it was discovered, the specific contents of the evidence, the name andaddress of the possessor, the name of the officer in charge of the analysis, and so forth. Publicprosecutors and assistant investigators who are engaged in investigating the case are able toaccess this data from their official PCs at any time.
3.

Digital Forensics
Recently, with the progress of Information Technology (IT), important evidence that used tobe recorded on paper is now being stored on computers as electronic data. It is necessary to seize
and analyse the data in computers thoroughly for successful investigation.

6

Objects to be found and seized, role-sharing of investigators, chain of command and communication among themembers, logistical matters, such as time and place for gathering, transportation of personnel, vehicles for conveying
seized evidence and arrangement of locksmiths, and so forth.

- 78 -

(i) Current problem
Successful seizure and analysis of electronic data requires the proper equipment, knowledge
and skill in the field of digital forensics. 7 Moreover, investigative authorities have to keep up todate with IT which is advancing day by day. However, in Japan, most prosecutors do not havesufficient technological knowledge or skills; they are legal professionals but not computer or IT
experts. Most assistant investigators are in a similar situation. Moreover, budgets limit the ability of
public prosecutors’ offices to maintain to up-to-date technology, because technology is developing
rapidly at high cost.
(ii) Measures in response
Public prosecutors’ offices are under pressure not only to recruit efficient investigators who
have good technical knowledge and computer skills but also to educate assistant investigators indigital forensics. The SID of the Tokyo District Public Prosecutors’ Office has a “Digital Forensic
Section (DFS)” which has computers for forensics and five or six efficient assistant investigators
who are devoted to the analysis of digital forensic evidence. They are selected from the pool ofassistant investigators that work in prosecutors’ offices all over Japan, and from those who havedeveloped the greatest knowledge and skill in the field of digital forensics.
Moreover, in Japan, there are some private companies which specialize in digital forensics incriminal cases.8 Public prosecutors’ offices work closely with them in conducting digital forensics
investigations and educating prosecutors and assistant investigators. In the SIDs, the DFS basicallyanalyses the digital evidence by itself; however, there is some digital evidence which requires
greater skill and forensic technology to analyse than that possessed by the prosecutors’ office. Inthat case, the SID asks the companies to analyse the evidence. Also, training in digital forensics forassistant investigators is conducted with the support of these private companies. In this sense, notlimited to the digital forensics field, cooperation with the private sector often strengthens theinvestigative ability of the authorities.
B. Interrogation of Suspects
1. Importance of the Interrogation of Suspects
Usually, there are no eyewitnesses or other items of physical evidence that are foundduring the investigation of corruption cases because of the secretive nature of the crime. Even
if we collected much physical evidence, it is necessary to explain what it means, but there arealso many cases in which the only persons who know the facts are the offenders themselves.
Therefore, obtaining confessions from suspects is vital. It is not too much to say that the bestand strongest evidence which proves the corruption offence is the confession of the offenders.
(i) Current problem
In Japan, confessions of suspects given during interrogation by police officers or publicprosecutors must be done without threat, assault or any other unlawful means in order to beadmissible as evidence at trial. 9 As defence attorneys are not permitted to be present at theinterrogation of suspects, disputes often arise at the trial between public prosecutors anddefence attorneys about whether the confession given during the interrogation was done7

For example, during a seizure operation, investigators are faced with the problem of how to seize data, including
deleted data; in some cases the computer must be seized, but in others it is enough to copy the data. In the analysis stage,
we have to analyse not only the data which remains on the hard disk but also the data which has been deleted. Deleted
data can often be obtained by means of data restoration technology.
8
They have the high confidence of the investigative authorities because they are highly specialized and maintainconfidentiality in their work.
9
If a suspect is compelled to confess by threat or assault by an interrogator, the confession is inadmissible as evidence
at trial regardless of whether the confession is true or not.

- 79 -

without any unlawful means. 10 It used to be sometimes difficult for prosecutors to prove thatthe confession was given without any unlawful influences because no neutral witness waspresent during the interrogation.
(ⅱ) Measures in response and further challenges
The SIDs introduced the system of video recorded interrogation of suspects in 2011.11
Currently, in cases where defence attorneys argue that prosecutors acted unlawfully during
interrogation, prosecutors can easily prove that their conduct was lawful by submitting thevideo to the court.
On the other hand, video recording presents new challenges. By introducing a video
recording system, suspects are reluctant to confess on camera. Moreover, before introducing
the video recording system, no one knew how each prosecutor interrogated suspects. But now
prosecutors are able to learn how other colleagues interrogate suspects by watching the videos.
It exposes the fact that there is so much difference among prosecutors about the way ofinterrogating suspects; while there are many proficient prosecutors, there are also poor
prosecutors who are poor at interrogating suspects.
One of the reasons why such differences exist is that there was no specific training
system or manual about the method of interrogation in Japan; that is, it was said that the skillof interrogation was learned through on-the-job training (or personal experience) of eachprosecutor. Prosecutors’ offices are beginning to seek good interrogation methods andtraining systems to enhance the ability of prosecutors to conduct effective interrogation ofsuspects even under video recording. 12
C. International Cooperation — Mutual Legal Assistance (MLA)
Globalization has made corruption crimes more and more sophisticated and cross-border innature. Corruption offenders tend to hide the assets obtained through crime in overseas bankaccounts which highly protect customers’ information from public officials; sometimes theconcealment of the assets is accompanied by money laundering. Hence, to investigate corruption
crime, the importance of international cooperation, especially Mutual Legal Assistance is rapidly
increasing.
(i) Framework of MLA in Japan
Japan can render MLA without an MLA Treaty (MLAT) or MLA Agreement (MLAA) as
long as there is a guarantee of reciprocity. If there is no MLAT or MLAA, the request has togo through diplomatic channels. On the other hand, if there is an MLAT or MLAA, therequest can be sent directly between central authorities of each country. In Japan, the Ministryof Justice (MOJ) and the National Police Agency (NPA) can both send requests as central
authorities, but the MOJ is the only central authority authorized to receive requests. 13, 14
10

Defence attorneys often insist at the trial that the confession of the accused given during the interrogation is notadmissible as evidence because it was given under assault or threat by the prosecutors.
11
Video recording interrogation by prosecutor, itself, begun from 2006, which is firstly limited to serious crimes, suchas murder, arson and so forth. After that, the cases investigated by the SID were to be subject to video recording
interrogation beginning in 2011.
12
Some advanced countries have the methods of interviewing or interrogating suspects, such as the PEACE Model in
the United Kingdom and the REID Technique in the United States, respectively.
13
If there is an MLAT or MLAA, Japan’s treaty partners are to send their requests to the MOJ, but they may receive
Japanese requests from either the MOJ or the NPA.
14
UNAFEI held the Sixth Regional Seminar On Good Governance for Southeast Asian Countries from 12-14
December 2012 on the theme of “International Cooperation: Mutual Legal Assistance and Extradition”. In this seminar,- 80 -

(ii) Capacity building of prosecutors in the field of MLA
In Japan, public prosecutors usually do not have any knowledge or experience in the
MLA field. Therefore it is very important to establish a training system for prosecutors toenhance the use of MLA; the on-the-job training system is working well.
The MOJ has an International Division in the Criminal Affairs Bureau, which is in charge of
MLA matters, where there is a Director, Deputy Director and four to five prosecutors. The
prosecutors of the International Division are selected from those who have around seven to ten
years’ experience as a prosecutor in each district public prosecutors’ office (It is not required forthem to have knowledge of MLA), and they can acquire sufficient knowledge and experience oninternational cooperation and mutual legal assistance through their work for two to three years.
After that, most of them go back to the District Public Prosecutor’s Offices, and they are expected
to play important roles in the field of international cooperation.
(iii) Utilization of informal channels in MLA
It is said that MLA, regardless of whether conducted using an MLAT or MLAA, takes a longtime to get the necessary assistance because of complications of formal procedure. To avoid this,the MOJ in Japan has been strongly recommending its foreign counterparts to engage in informal
consultation before sending a formal request, even if the request is non-treaty based.
Utilization of informal channels is an effective measure in MLA to get necessary information
quickly because it enables the flexible exchange of information. Constant effort for establishing
informal channels among foreign countries is very important to expedite MLA.
In Japan, some prosecutors work not only at the International Division of the MOJ, but they
are also dispatched as first secretaries to embassies of Japan, such as in the USA, UK, France,
Germany, Korea, China, and so forth. They work for around three years in the legal section of theembassy, and are in charge of MLA matters between Japan and the country that they have been
dispatched to. They are able to not only gain expertise about MLA of Japan and the country they
were dispatched to, but also make contact with important government officials. The networks they
make are working well as informal channels in MLA.
(iv) MLA in the field of investigation of corruption cases
It is crucial for investigative authorities of corruption cases to allocate investigators who haveenough knowledge and experience in MLA to expedite MLA in their investigations. The SID of
the Tokyo District Public Prosecutors’ Office has a prosecutor who not only has great knowledge
and experience in MLA but also a wide network functioning as informal channels. In situations
where Japan requests MLA from foreign countries in the process of investigation of corruption
cases committed by politicians and high-ranking officers, he or she rapidly takes necessary
measures in cooperation with the International Division of the MOJ’s Criminal Affairs Bureau,
making the most of informal channels.
III. CONCLUSION
To tackle corruption offenders who use various methods to tamper with evidence, thecollection and analysis of objective evidence and effective interrogation of suspects are both
crucial to discovering the the truth. As it were, these measures are like a pair of wheels that
Mr. Masamichi Kamimura, Director of the International Division of Ministry of the Criminal Affairs Bureau of theJustice, presented on MLA and extradition in Japan. <http://www.unafei.or.jp/english/pdf/PDF_GG6_Seminar/041_SP1.pdf>.

- 81 -

when properly working together produce the desired result. Moreover, to cope with theglobalization of corruption cases, the importance of international cooperation is increasing
more and more. UNAFEI hopes that this seminar establishes informal channels to facilitate
international cooperation in the future.

- 82 -