Japan's Supreme Court will launch studies into the current record-keeping process of trial records after a family court discarded all documents of a serial murder case involving a teenager 25 years ago.

Rules regarding juvenile cases state that records of investigations and trials, as well as those on minors' upbringing, must be kept until the offenders reach the age of 26.

As for cases that had a social impact, the Supreme Court's rule instructs courts nationwide to permanently keep their records.

But it has come to light recently that a family court in the western city of Kobe discarded all records of the case of a serial murder committed by a teenage boy in 1997.

Records of the murder of a sixth grade girl by her classmate in Nagasaki Prefecture in 2004 were also disposed of.

Supreme Court officials say rules were not followed, and records which needed permanent preservation were discarded. They will seek the opinions of outside experts, and study whether recordkeeping has been done appropriately.

The officials plan to ask experts to evaluate the current method of selecting cases for permanent preservation, as well as whether the staff at the courts were aware of such record-keeping rules.