The next day he bought a one-way ticket to Brisbane and within 24 hours of the crash, he had left New Zealand, the Crown said.
Pierce voluntarily returned from Australia months later to face police charges. He was arrested when he landed at Christchurch International Airport on January 6 last year.
Pierce denies causing Mr Frost's death between October 27 and November 1 in 2012 by carelessly driving while under the influence of drink to such an extent "as to be incapable of having proper control"of the 4WD Toyota Landcruiser.
He also denies an alternative charge that he caused Mr Frost's death by carelessly driving while under the influence of drink "in a matter that is not an offence against the Land Transport Act"; and that as a driver involved in an accident where someone was killed or injured he failed to stop and ascertain injury and give "all practicable assistance".
Crown prosecutor Anselm Williams told a jury of eight men and four women that Mr Pierce had been drinking bourbon and cola mixers since about 3pm that day at a party.
Fellow partygoers will give evidence during the week-long trial that he had been showing "signs of drunkenness", Mr Williams said.
About 9pm he was driving with Mr Frost on the rural road near West Melton when he failed to take a moderate bend on the approach to a T-intersection.
Pierce, a disqualified driver at the time, went onto the grass verge, narrowly missed a power pole, crossed the intersection and hit another power pole.
Mr Frost was seriously injured.
Pierce got out of the car and walked to his friend's vehicle, which had been following behind, the court heard.
"The accused demanded that [the friend] take him away from the scene immediately," Mr Williams said.
He said they took Mr Frost out of the vehicle and laid him on the ground beside it.
The sound of the crash brought some locals out to investigate.
Pierce denied being the driver, the court heard, and allegedly told locals that he had just come across the crash and that Mr Frost had been driving.
He allegedly told a member of the public that he had phoned emergency services, but Mr Williams said there was no evidence that he had.
Pierce's friend drove them away from the scene, Mr Williams said.
It is alleged that within half an hour, Pierce sent a text to a friend in Australia, indicating that he was going to fly to the Gold Coast.
The Crown does not allege that Pierce -- who was not breath tested or had a blood sample taken before he left for Australia -- had been over the limit at the time of the crash.
It alleges that he was under the influence of alcohol to such an extent that he had no proper control of vehicle at the time of the crash.
Mr Williams said there would be evidence that Pierce had "consumed a significant quantity of alcohol"that night, and he would show the jury a text to Pierce's girlfriend at 7pm which said he was "drunk".
Defence counsel Richard Maze elected not to give an opening address.
The trial, before Judge Alistair Garland, continues.
