The Supreme Court on Friday upheld the death sentence of a 52-year-old man who murdered a former top health ministry bureaucrat and his wife and attempted to kill the wife of another chief bureaucrat in a 2008 stabbing spree that stunned the nation.

Presiding Justice Tsuneyuki Yamamoto turned down Takeshi Koizumi's appeal of the Tokyo High Court's 2011 ruling, which upheld the lower court ruling on his sentence.

According to the ruling issued by the Saitama District Court in March 2010, Koizumi stabbed to death Takehiko Yamaguchi, then 66, and his wife, Michiko, then 61, with a kitchen knife on Nov. 17, 2008, at their home in Saitama. Yamaguchi had formerly been administrative vice minister at what was known as the Ministry of Health and Welfare, which became part of the Health, Labor and Welfare Ministry.

The following day, Koizumi attacked and seriously injured Yasuko Yoshihara, the wife of another former top health bureaucrat, at their home in Tokyo's Nakano Ward.

Justice Yamamoto said in the ruling that the defendant spent a long time picking his targets, making detailed plans about the weapons he would use and his method of attack. He also said the defendant stabbed them several times in a cruel manner.

During the court hearings, the defendant argued that he attacked the victims to avenge his pet dog, which was put down at a public health institute when he was a child.

Koizumi's defense counsel had urged the top court to refrain from issuing the death penalty, noting the defendant was suffering from mental disorders at the time of the attacks.

During his trial at the Tokyo High Court, Koizumi pleaded not guilty, saying he had killed not humans, but evil entities.