Stopping a mate from driving drunk makes you a "bloody legend'', according to the television ads.
But a Cromwell man found it was not quite that simple when his mate stabbed him in the left arm six times as he tried to grab his car keys.
The victim collapsed in a pool of his own blood and was airlifted from Central Otago to Dunedin Hospital in a critical condition where surgeons worked to save his limb.
He would be doing "extremely well"' to eventually have his arm functioning at 50 per cent, a specialist said.
Since the incident the man had lost his marriage and his job as a diesel mechanic.
"You have ended the victim's life as he knows it,"' Judge Kevin Phillips said in the Dunedin District Court yesterday.
Craig Lisle Wadsworth, 42, appeared on a charge of wounding with reckless disregard.
The pair, who had been friends for more than 20 years, met at the victim's house for his going-away party on June 17.
The victim was moving to Dunedin to begin a new job.
But just hours later, any hopes of a fresh start were obliterated.
"Out of the blue'', Wadsworth punched his friend in the face while they were drinking in the garage.
Another reveller intervened to stop them wrestling and the defendant stormed off to his
Toyota Hilux, which he had parked in the drive.
Earlier, he had given his car keys to the victim's wife but she was unaware he had a spare set.
Wadsworth revved the engine and reversed at speed, twice hitting a fence, before stopping.
The victim approached and reached into the half-open window to take the keys out of the ignition.
"The victim had the defendant's best interests at heart," counsel Bill Dawkins said.
But he said his client, in his drunken state, believed the man was seeking retribution for the violent outburst moments earlier.
Wadsworth grabbed a hunting knife from the central console, took it out of its sheath and began "furiously stabbing" the victim's left arm.
He wounded the man five times between the elbow and hand and struck another blow to his right wrist.
During the attack, Wadsworth sliced through nerves, tendons and an artery, and on one
occasion his knife went right through his friend's arm.
While the man collapsed metres away, the defendant remained in the vehicle.
"He was yelling and screaming obscenities and smashing his fists up and down on the
dashboard," the police summary said.
Wadsworth then drove home and disposed of the weapon, which was never found.
He initially told police his actions were in self-defence and he had used a butter knife, before later admitting what happened.
The court heard how Wadsworth's wife had recently given birth to their second child and he had a job waiting for him if he was not jailed.
Crown prosecutor Marie Grills said the seriousness of the incident should draw a period of imprisonment but Judge Phillips was persuaded to stop short of that.
He said Wadsworth was "totally out of control'' and exhibited a high degree of recklessness, but said home detention was enough to denounce his conduct and to deter future offending.
The 42-year-old will spend the next nine months at his Cromwell home and was sentenced to 250 hours' community.
Wadsworth was also ordered to pay the victim $5000.