Japanese prosecutors have informed a court of their plan to seek a conviction in a retrial for an 87-year-old man who was convicted of killing four people 57 years ago.

The prosecutors on Monday conveyed their decision to the Shizuoka District Court, which will hold the retrial for Hakamada Iwao.

Hakamada was sentenced to death for killing a family of four in Shizuoka Prefecture, central Japan, in 1966. He had pleaded innocent and requested a retrial.

In March, the Tokyo High Court decided to grant a retrial. It said investigators likely fabricated key evidence and argued that there was clear evidence that would lead to an acquittal.

Ahead of the retrial, representatives of the district court, the defense team and the prosecution have been holding three-way talks since April. The defense lawyers asked prosecutors not to seek a conviction, but the prosecution has decided to seek a guilty verdict against Hakamada.

The key point of contention is the color of blood stains on clothes that allegedly belonged to Hakamada. The clothes were found in a tank of miso soybean paste more than a year after his arrest.

Prosecutors say there is no indication that the stains on the clothing were faked. They say that it is entirely possible that the stains persisted and retained a red hue even after a year immersed in miso paste.

Defense lawyers plan to lodge a plea of innocence, saying that the clothing items should be excluded from evidence as they did not belong to Hakamada and were fabricated.

The prosecutors' decision to try to establish guilt in the retrial means the legal proceedings will likely be prolonged.