Aggravated careless driving causing injury or death carries a maximum penalty of three years in jail or a maximum fine of $10,000 plus mandatory disqualification from driving for one year.
The mandatory disqualification from driving on a charge of careless driving causing injury or death is six months.
Crown prosecutor Kyle MacNeil's application for leave to amend the charges was not opposed by defence lawyer Anthony Rogers yesterday.
The pleas were entered the day Stewart's four-week trial was scheduled to start in the Whangarei District Court.Stewart caused the deaths of his wife, Susanna Stewart, 48, their daughter Sadie, 16, and friend James Wearmouth, 18, who were on their way home from Baylys Beach with other members of the Exclusive Brethren community near Dargaville.
There were eight passengers in the five-seater Mitsubishi Triton and Stewart was behind the wheel. He was remanded at large until February 23 for sentencing in the same court.