A Japanese high court upheld Monday a sentence of 18 years in prison for a man convicted of a 2017 road rage incident that killed a couple and injured their two children and caused an outcry that led to tougher punishment of dangerous driving.

The Tokyo High Court rejected the appeal of Kazuho Ishibashi, 32, who was convicted of dangerous driving at a lower court for forcing the car of Yoshihisa Hagiyama, 45, and his family to stop on the passing lane of the Tomei Expressway in Kanagawa Prefecture, near Tokyo, on June 5, 2017, where it was rear-ended by a truck.

Extensive news coverage of the incident sparked greater public concern over dangerous driving. In 2020, the government enforced revisions to Japan's traffic laws that toughened punishment for road rage offenses.

According to the Yokohama District Court's ruling in June 2022, Ishibashi was enraged after being warned by Hagiyama about the way he had parked his car in an expressway parking area just before the incident. Ishibashi pursued Hagiyama, who was traveling with his 39-year-old wife Yuka and their two daughters.

Ishibashi drove directly in front of Hagiyama's car four times and repeatedly engaged in obstructive driving by slowing down and approaching close to Hagiyama's vehicle. Hagiyama subsequently took the risky action of stopping the car on the highway before being rear-ended by the truck.

File photo shows a damaged vehicle being towed on the Tomei Expressway in Kanagawa Prefecture in June 2017 following a road rage incident that killed a couple. (License plate pixelated)(Kyodo)

The defendant was handed the 18-year sentence at his first trial at the Yokohama District Court in December 2018. After an appeal, the Tokyo High Court in 2019 upheld the decision but quashed the ruling and sent the case back on a technicality, citing an illegal procedure by the lower court.

The high court said the district court, in handing down the ruling, had illegally overturned the view it had expressed in a pre-trial process that Ishibashi's actions did not constitute dangerous driving.

In the retrial held at the lower court in June 2022, Ishibashi was again sentenced to 18 years in prison and he once more appealed.

The revised road traffic law that came into effect in June 2022 defines road rage as "obstructive driving," and says it includes aggressive tailgating and horn use. It is subject to penalties of up to five years in jail or a maximum 1 million yen ($6,600) fine.

Driving on the wrong side of the road, sudden braking and weaving between lanes in an aggressive manner are among other dangerous acts that can be categorized as road rage.

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