They had planned to drive south through the North Island and then on to the South Island and were leaving Waitomo when tragedy struck.
"A few days into this the defendant made a driving error, a very serious one," said his lawyer, Philip Morgan, QC.
Smith made a u-turn in the Ford campervan he was driving, into the path of a northbound truck-and-trailer unit at the intersection of SH37 and SH3 at Hangatiki, about 10km east of Waitomo.
The truck driver was unable to avoid the collision and ploughed into the front left of the vehicle.
Mrs Smith, 62, who was sitting in the front passenger seat, suffered critical injuries and died at the scene.
Smith and their 24-year-old daughter, who was sitting in the rear, suffered minor bruising. The truck driver was shaken but unscathed.
Mr Morgan said "one may question" why it was relevant to convict.
"He [the defendant] is of course torturing himself over having caused the death of his wife and mother of his children. There's nothing anyone can do to penalise him more than he already has been."
Mr Morgan then revealed as an "illustration of how mean life can be" that the Hamilton hotel room of Smith and his family was burgled the night before his appearance.
They lost three cellphones, an iPad, headphones and a backpack.
"This family has had enough," said the Queen's Counsel.
He said Smith was an experienced driver, who had operated heavy road machinery for much of his life and had driven in other countries that drove on the left-hand side of the road.
But he admitted his client's driving on the day of the accident was inexplicable and careless.
"All they want to do is get back on a plane and fly back to Canada so they can attend to funeral arrangements."
Community Magistrate Wilson said the maximum punishment for the offence was a three-month prison term, disqualification from driving for six months and a $4500 fine.
But she said no punishment could restore the loss to Smith and his family and took into consideration his co-operation with police and immediate guilty plea.
"I have little doubt that you are totally horrified in finding you have killed someone; this will remain with you forever. This was just a lapse but it had enormous consequences."
As she sentenced Smith to a six-month driving disqualification and ordered him to pay court costs of $132.89, his two daughters and his stepsister hugged one another and cried in the public gallery.
Neither Smith nor any of his family would comment after his appearance. The Herald understands the group was led away by police through a rear court exit.
The crash at that highway intersection was the third serious accident involving an overseas driver since February 2009.
But Transport Agency Waikato/Bay of Plenty state highways manager Kaye Clark said improvements had been made at the intersection, including a longer slip lane, the construction of traffic islands, new lighting, bank trimming and tree removal to increase sight distance.
