Many records of landmark civil cases in postwar Japan no longer exist, having been disposed of by courts across the country, according to Kyodo News findings released Sunday.

Almost all judgments in the cases investigated have been preserved, but most of the other documents related to hearings during their trials were not, resulting in a loss of history.

The cases scrutinized totaled nearly 140 and revolved around such issues as nationality, freedom of expression, separation of state and religion, expropriation of land for national defense, and the constitutionality of the Self-Defense Forces.

Japanese regulations stipulate that important court documents must be preserved by district courts, and experts say that their destruction may be potentially illegal.

Kyodo News looked into 137 constitutional civil cases of which 118, or 86 percent, had their documents relating to their judicial procedures discarded. Only 18 cases had all of their documents preserved, while the status for one case is currently unknown.

Under the regulations, documents that "should be historical records or reference data" must be "under special preservation." However, even among the 18 cases, only six had measures taken to ensure they received special treatment and one was sent to the National Archives of Japan.

District courts are usually supposed to preserve records for five years after a decision or resolution of disputes is made. Decisions are supposed to be preserved for 50 years.

It was previously known that some records of famous cases were discarded by the Tokyo District Court, but this is the first time that the national extent of this practice has been revealed.

One of the cases involved a 2008 Supreme Court decision that ruled a nationality clause unconstitutional. The case was brought by Filipino women who sought citizenship for 10 children born out of wedlock with Japanese fathers.

A 1982 court case lasting nine years pitted residents of Naganuma in Hokkaido against the government, which sought removal of an area from a designated forest reserve to build a missile base.

Although the Supreme Court ultimately ruled in favor of the government, the case was important in that the Sapporo District Court ruled that the SDF was unconstitutional.

Another case was a court fight between the Okinawan prefectural government and the central government over private land to be used for U.S. military facilities. Gov. Masahide Ota refused to renew the agreement allowing such use in 1995 amid residents' anger over the rape of a 12-year-old local girl by U.S. servicemen.

Although the governor ultimately lost under the top court's ruling, the case was another example of the tense relationship between Okinawa and the central government over U.S. military bases.

The top court, in response to Kyodo News questions, said "it is each court's individual decision" to determine whether to dispose of such records.

However, it seems to recognize the importance of preservation, citing "increasing societal interest in the historical value and in the necessity of preserving archives, including public and official records."

Individuals related to or affected by the cases have expressed disappointment, with a lawyer in the Okinawa court case saying that the records were "the property of the people."

"Most historical court cases are fought all the way up to the Supreme Court. It is perhaps necessary to have a system where the Supreme Court, which can determine the importance of the court cases, tells the district courts which records to preserve," said Eiji Tsukahara, a law professor at Aoyama Gaukin University Law School.

"In the United States, it is understood (that record preservation) is necessary to protect freedom and democracy. In Japan, there will need to be more such understanding," said Hiroshi Asako, a Waseda University emeritus professor who is an expert on judicial record preservation, while acknowledging the cost associated with it.