"I'm not in any way responsible for the death of my wife. I'm totally innocent. I had no reason to kill my wife," Robert Lund, 59, told the court at the start of the trial in the southern French town of Montauban.
Lund was sentenced to 12 years in jail in 2007 for the involuntary homicide of his wife Evelyn, whose body was found in a lake in 2002, two years after she disappeared from their home in southwestern France.
An appeals court upheld the verdict in 2009 but his third trial comes after he appealed on a point of legal procedure.
Lund reported his 52-year-old spouse as missing in 2000, on New Year's Day, telling investigators he believed she had an accident after drinking heavily and setting off to visit friends.
Despite an extensive search, Evelyn's remains were not found until nearly two years after her disappearance.
Her body was found inside her car in Lake Bancalie, between the Lund family home in the village of Rayssac and that of the friends she was alleged to be visiting.
The Lunds had moved to the region, home to a large British expatriate community, in 1997.
Evelyn's three daughters brought the case against Lund, who has always protested his innocence.
Lund's lawyer, Apollinaire Legros-Gimbert, said there were enough uncertainties in the case, including over the cause of Evelyn's death, to raise hopes of an acquittal.
Legros-Gimbert admitted that his client was taking a risk with the new trial as he could be found guilty on the more serious charge of murder and face even longer in prison.
He said the fact Lund was willing to take that risk was evidence of his innoncence.
But a lawyer for Evelyn's family, Henri Renier, said Lund was seeking an acquittal in order to inherit her estate and proceeds from her life insurance, which were blocked when he was convicted.
By seeking a new trial Lund has subjected the family to "a final ordeal," Renier said.