Appearing for Shepherd, solicitor Ian Hard said Shepherd had been drinking at Toast Martinborough with friends and had made "a ridiculous decision to drive home".
He had only driven 100m on Ponatahi Rd before being stopped by police and tested.
Mr Hard said while Shepherd - facing his first court appearance - was "very remorseful" he was also very grateful to police for stopping him before something else happened.
"Clearly, he should not have been on the road," Mr Hard said.
He had asked Shepherd whether he had a drinking problem and had been assured that was not the case, said Mr Hard.
"He is normally a moderate drinker with an impeccable record until now."
Judge Davidson fined Shepherd $1100, ordered him to pay a total of $424.60 in tests and medical expenses and disqualified him from driving for eight months.
In court on the same day last week was Michael Blaine MacGregor, 21, also of Carterton who pleaded guilty to drink-driving having returned a breath alcohol reading of 982mcg per litre of breath when stopped in Kent St, Carterton, on November 23.
The legal limit is 400mcg.
Mr Hard appeared for MacGregor and said the offence was "an aberration".
He said MacGregor had been fully co-operative with police and had no previous history of drink-driving.
Judge Davidson fined MacGregor $700 and disqualified him from driving for seven months.