"But it's not unlimited power. [Police] are bound by the Bill of Rights Act. People have a right to be safe from unreasonable searches."
He said the fact police had received a tip-off further justified their right to search her belongings.
People were generally considered to have a "lesser expectation" to privacy in a car than in a house, he added.
Carroll also argued the 3 -year sentence was too harsh, given her life had been turned upside-down by the death of her partner.
She had been returning from a visit to his grave in Auckland when the car crashed.
Carroll's adult daughters submitted references to the court to support their mother.
Her youngest said: "We consulted with various drug advisory [groups] but those that we spoke with said it was up to the individual to admit they have a problem and seek help. I honestly felt that not only did I lose my father that year but my mother as well."
The daughter said Carroll had spent $200,000 from the sale of the family home, within 10 months.
"She decided to sell our family home which she had fought tooth and nail to keep over the years," she said.
Her eldest daughter said: "It all went downhill from there."
In his judgment, Justice Wild said the original conviction and sentence were appropriate and dismissed Carroll's appeal.
