The truck driver who killed four police officers when he crashed a 19-tonne semi-trailer into them on Melbourne's Eastern Freeway has had his jail sentence slashed on appeal.Mohinder Singh, 49, was sleep-deprived and high on drugs when he veered into a service lane and crashed the truck into the Victoria Police officers, who had pulled over Porsche driver Richard Pusey for speeding.The 22-year jail sentence Singh had been dealt for the crash in July 2021 was cut to 18 years and six months' jail