One of the major causes of wrongful conviction in Japan is definitely false confessions.
Why? Obviously, since a confession is still the “King of evidence” in Japan. And since the law permits a long period of detention (23 days!) before the formal charge (indictment) of a suspect, and since during this pre-charge detention period, there are lengthy interrogations by the police and prosecutors.
When and How Long can a Suspect be Detained?
In Japan, a suspect can be detained when there is a “reasonable cause” that he/she committed the crime, and there is a risk of flight or he/she might tamper with the evidence in the case. When a judge issues an arrest warrant and once the suspect is arrested (“Taiho“), the police has 48 hours to transfer the suspect and the case to prosecutors.
When prosecutors receive the suspect and if they think he/she should be detained further, they must ask a judge within 24 hours of receiving the case to issue a warrant for up to 10 days of additional detention (“Koryu“). This is when the suspect appears before a judge for the first time. Additional 10-day extension of Koryu is possible after the initial 10days. Judges almost always issue the arrest/ detention warrant. Less than 1 % of the warrant claim is denied. For violent crimes, it’s almost 0%.
To sum up, police and prosecutors can detain a suspect for up to 72 hours before the suspect has to appear before a judge, and then for additional 20 days before the formal charge (23 days in total!).
Interrogation During Detention
During this 23-day period, police and prosecutors usually interrogate the suspect for a long period of time. Conducting the interrogation is critical, even for prosecutors.
The interrogator summarizes the content of the interrogation and writes it down into a statement called dossier (“Chosho”). The interrogators are not required to record the suspect’s words verbatim. The dossiers are often criticized as being the “interrogator’s essay”. The long dossiers, when they are made by prosecutors, can be easily introduced as evidence at trial as an exception to the hearsay rule.
At the beginning of the interrogation, suspects are advised of their right to remain silent, but the interrogation does not have to stop even if the suspect chooses to remain silent. Even if he has a lawyer (for more serious offenses, the suspect has the right to a court-appointed attorney during the pre-charge detention (koryu) period), it is extremely rare for the lawyer to be present at interrogation. The police and prosecutors even retain that once the suspect is arrested and detained, he/she has the duty to be interrogated.
The police and prosecutors in Japan have not agreed to the recording of the entire interrogation process. They have in fact started recording parts of interrogation from 2009, but it is still a partial recording (read about this here and here).
Where are Suspects Detained?
In addition, during the pre-charge detention, the majority of suspects are held in so-called Daiyo-Kangoku or Daiyo-Keiji Shisetsu, Japanese words for “substitute prisons” or “police jails”.
What happens in a police jail? In sum, the suspects are easier to interrogate because they are in the hands of the police. Interrogation continues until the suspect finally makes a confession. Surprisingly, for the 23 days before charge, the suspect does not have the right to bail.
Even if the Suspect is not detained, the police and prosecutors can interrogate him/her “voluntarily“. When the condition for arrest or detention is not met, the investigators still ask the suspect to come to the police or prosecutor’s office “voluntarily” and interrogate him. The Supreme Court permits this tactic as long as it is done in a reasonable manner and does not exceed a reasonable limit.
So what is this reasonable manner and limit?
There is a notorious case called the Takanawa Green Mansion Case that set the standard. It was a murder case. The suspect in the case was voluntarily taken to a police station on June 7th at 10:00 in the morning. He was interrogated until 23:00 of the same day. The police made him stay at a nearby hotel with 4 police officers on watch. The interrogation continued until June 11th, daily from 8:00 am to 23:00. The suspect never explicitly asked the police to go home. Was the 4 nights and 5 days of voluntary interrogation in this case legal?
Yes, said the Supreme Court on February 29th, 1984. The Court said the interrogation was not appropriate, but was legal. The suspect never explicitly asked to go home, hence the interrogation voluntary.
For the same reason, the Supreme Court affirmed a 22 hour-long interrogation in 1989 (Hiratsuka Waitress Murder Case).
False Confessions as Major Cause of Wrongful Convictions
Not surprisingly, under these circumstances, there are a lot of false confessions obtained from hours of interrogation. You can see many cases of false/ forced confessions, including the Ashikaga Case, Higashi-Sumiyoshi Case, Hakamada Case, Nabari Case, and Teigin Case, and these may only be the tip of a huge iceberg.
I think false confessions are the major reason for wrongful convictions in Japan. And maybe it is us, the public, who still hold this system of long detention and interrogation, who should be blamed.
Read more (in English) about this topic in: David T. Johnson, The Japanese Way of Justice – Prosecuting Crime in Japan (Oxford Univ. Press, 2002), esp. Introduction and Chapters 1 & 8.