Warrick Delaney Taylor (23) smoked the drug before he gave his mate a lift from Oamaru to Dunedin on June 3 last year and he did so while on the return leg too before tragedy struck.
"A tragedy you manufactured," Judge Kevin Phillips said.
Driving his friend’s unwarranted, unregistered car, Taylor veered across the centreline and crashed head-on with 64-year-old Stuart Ernest Windle, who was leading a convoy of vehicles travelling to a car rally.
The defendant was charged with careless driving causing death and five counts of careless driving causing injury, all of which hold a maximum penalty of three months’ imprisonment.
He was jailed for five months before the Dunedin District Court yesterday.
Janice Beckett, who was driving behind Mr Windle and his wife when the collision occurred, said it was simple.
"The police have mucked up," she said.
"We don’t think justice has been done."
Judge Phillips said a sample of Taylor’s blood was taken after the crash and tested positive for THC — the active ingredient in cannabis.
But he said the sample was not tested for the level of the drug.
Police previously released a statement in which they stood by the level of charge.
"The investigations into the crash went through the Police Serious Crash policy, which was then reviewed by the legal team at Police National Headquarters in Wellington. Following this, the appropriate charge was laid based on the evidence to hand," it said.
Taylor’s lawyer Andrew Dawson said his client wanted to go to prison for what he had done.
"He believes that would be a fair result for what he’s done," he said.
Family members of Mr Windle said it should have been Taylor who was killed in the crash and the defendant agreed.
"That’s very clearly his view," Mr Dawson said.
He had been using alcohol and cannabis regularly during the period but had abstained since them and had vowed never to use them again.
"It has weighed very heavily upon him," Mr Dawson said.
Mr Windle’s family also spoke about the overwhelming impact the fatal crash had had on their lives.
His wife Glynis told the court they had been all set to celebrate their 42nd wedding anniversary just days after the crash.
"I’ve been deprived of a life we planned and were looking forward to in retirement," she said.
The Kaikoura couple had been planning to settle in Christchurch and on the day of the crash concrete had been poured at the site of their new house.What hurt most, Mrs Windle told the court, was the fact she had been robbed of saying a final goodbye to her husband.
"How proud I was of the life we shared together," she said.
The couple were planning a trip to Brisbane a couple of weeks after the crash to see friends.
Instead, those friends came to New Zealand for the funeral.
Mr Windle’s daughter Janelle — mother of his three grandchildren — labelled Taylor "scum".
'He murdered my dad and should be locked away for life," she said.
Judge Phillips said he would have jailed Taylor for longer if the law had allowed him.
"Overall your attitude and driving conduct was, in my view, totally reckless," he said.
As well as the prison term, he banned the 23-year-old from driving for three years and ordered him to pay $2355 reparation.