At an inquest in Gore, Mr Crerar said he believed Troy MacFarlane Adamson felt bullied and threatened before leaving the party at a shearing quarters in the West Otago township of Heriot on February 19 last year.
"Troy was very intoxicated. His blood-alcohol level was seven times over [the then legal limit].
"He could very well have killed others in the state of intoxication that he was in."
Troy, who started working in Heriot for his uncle as a shearer in October 2010, was not authorised to drive the van.
He died just three months after his best friend was killed in a drink-driving crash.
Troy's father, Richard Adamson, said his son getting into a vehicle while intoxicated was out of character for the teen, who was still "cut up" about the death of his best mate.
"I had talked to Troy about drinking and driving. He had lost his best mate from drinking and driving in November."
Troy's mother, Kirsty MacFarlane, said some shearing gangs were just that, gangs.
"People should be upfront, and tell the truth. I feel annoyed that Troy will probably go down in the statistics as an underage Maori drunk driver. It was out of character for him."
Troy was described by several witnesses as a quiet teenager, who always wore his hair tied up under a beanie hat, and after a few drinks that night "came out of his shell", taking off his beanie and head-banging in time to the music like a guitar player in a metal band.
Mr Crerar said that after Troy was pushed, which caused him to fall over and break a table tennis table, he was further harassed.
"Troy was described as becoming quiet and drinking more.
"My point is that Troy was teased; some would call it bullying, some would call it harassment.
Some of this was due to his [long] hair."
One witness statement read to the court said people began teasing him, telling the teenager that if he fell asleep they would cut his hair. The comments were not malicious, the witness said.
Senior Constable Ken Patterson, serious crash investigator, of Invercargill, said Troy held an Australian learner licence and was not authorised to drive the vehicle, which was co-owned by his uncle, Dale Paikea - who was also his employer - and his partner.
The van's warrant and registration were out of date, but a mechanical examination of the vehicle found no faults that could have caused the crash.
Mr Paikea told the inquest the vehicle was a stock-standard van with no modifications.
"It was very powerful and I did not let any workers drive it."
After he finished giving his evidence, Ms MacFarlane addressed Mr Paikea, telling him her son was not just an employee, he was his nephew.
"Troy was a 17-year-old youth who was still a minor. You said in the police report Troy was not allowed to drink. With Troy being a 17-year-old youth, where was the supervision?"
Mr Paikea said he normally oversaw Troy's drinking, but was out of town that weekend.
Troy lost control of the Toyota van while driving at a speed of between 112kmh and 117kmh in Roxburgh St, Heriot's main street, which had a speed limit of 50kmh, Snr Const Patterson said.
The van crashed off a bridge and into a stream.
Sonny Paikea, also a shearer, and Troy's cousin, was one of the first people at the crash scene.
He learned Troy was missing after returning to Heriot from a birthday party in Millers Flat.
With friends, he went looking for his cousin. As they were driving along, someone saw brake lights under the bridge.
"We all went into the water. Troy was completely submerged.
"We flipped the van up to get Troy's head out of the water. I grabbed him to get his head out of the water."
The local volunteer fire brigade arrived and took over, cutting Troy's seatbelt to free him from the van.
Pathologist Dr Martha Nicholson said toxicology showed a high level of alcohol in Troy's blood and urine.
The very high level, of 213mg per 100ml of blood was more than seven times over the 30mg limit for his age, she said.
The 282mg level in his urine suggested Troy had stopped drinking and alcohol was leaving the body.
Dr Nicholson said cannabis was also detected in Troy's system and would "accentuate the effects of alcohol".
Troy was found trapped in the vehicle and not easily recovered from the wreckage.
The injuries he sustained were "predominantly superficial", and she found he died of positional asphyxia, in about three to four minutes.
