Background
In the final days of 2000 a family of four living in Kamisoshigaya, in Tokyo's Setagaya ward, lost their lives at home: a mother, a father and their two young children. Out of respect for their privacy, the victims are not named here, nor are details about the children given.
What happened
The killings took place overnight between 30 and 31 December 2000, with police placing the attack near midnight. A relative of the family discovered the bodies on the morning of 31 December.
It is known that the perpetrator stayed in the house for hours, ate, used the computer and took some money. He left behind a large amount of traces, including fingerprints, DNA and clothing.
Investigation
The case led to one of the largest criminal investigations in Japanese history, with tens of thousands of officers assigned over the years and thousands of pieces of evidence examined. The perpetrator's clothing and other items had been purchased in Kanagawa Prefecture. The shirt was reportedly made in only about 130 units, and police could trace just 12 buyers. His shoes were made in South Korea. DNA analysis suggests his father was of East Asian origin and his mother possibly of European origin. Yet none of this has led to a name.
No one has ever been charged. The case fuelled debate over statutes of limitations for crimes punishable by death, and Japan abolished such limits in 2010.
More than 12,000 pieces of evidence were recorded, and the number of officers who took part exceeded 240,000 in total. The shoes were found to have been made in South Korea and sold under the Slazenger brand. None of this matched the DNA or fingerprint databases held by police.
Where it stands today
The case is unsolved. A reward of around 20 million yen has been offered, police continue to appeal for information, and about 35 officers were still assigned to it in 2019. Police announced in 2019 that the house would be demolished. The case remains one of Japan's most cited examples of delayed justice.
Police continue to ask the public for information on any unusual person or vehicle seen in the area at the end of 2000.