The findings were to be confirmed by toxicological analyses, public prosecutor Samuel Vuelta Simon said, but Soledad Cabeza de Vaca Leighton was found to have been in a polypathological state and to have had a major pulmonary infection and the first results "excluded the intervention of a third party" in her death.
The autopsy was ordered after her 65-year-old son, Forester Labrouche, filed a legal complaint for voluntary homicide against person or persons unknown shortly after his mother's death on 29 November at her home in Bayonne, south-west France.
Battle with adopted son
The complaint was not the first filed by Forester Labrouche and his wife Stéphanie.
They have been contesting the management of the Marquesa's fortune, estimated at over 100 million euros, with her 38-year-old adopted son, German de la Cruz, for 20 years.
On 17 November, while de Vaca was still alive, they went to court to contest a mandate she had signed handing the management of her fortune to de la Cruz or, by default, her long-time money-manager, Swiss lawyer Markus Frey.
And in July they filed a case alleging illegal confinement and breach of trust as the Marquesa's health declined, particularly following the onset of Alzheimer's disease.
The cases were greeted with indignation by German de la Cruz, whom de Vaca adopted in Colombia when he was eight-years-old.
He accused his brother of not bothering to visit their mother for 20 years and trying to deny him access to the family home.
Labrouche accuses de la Cruz of preventing him visiting his mother in July and of firing his mother's governess and lifetime friend, who has supported the elder brother's case.
De Vaca's father was a Spanish nobleman, descended from a conquistador, Alvar Nunez Cabeza de Vaca (1488-1559).
But she inherited her wealth from her mother, Olga Leighton, a British national who had inherited it from her first husband, an American millionaire.
She herself invested in artworks, property and race horses, which appear to have been her principal passion.
The brothers started fighting over her fortune shortly after Forester Labrouche married Stéphanie, who was already comfortably off due to a career in banking and claims he was living in a small apartment in in Zurich and receiving a "a small remittance" from Frey.
The couple suspected Frey of exploiting de Vaca's wealth by setting up a number of companies and investment funds and charging for their management.
Frey's lawyers say that he has been cleared of any wrongdoing by courts in Switzerland and Britain and that Forester Labrouche has already received 60 million euros of the family fortune.
Parallels with Bettencourt case
In a long legal battle, her daughter, Françoise Bettencourt-Meyers, accused photographer François-Marie Banier and other members of her entourage of exploiting her mother for financial gain.
The Marquesa, however, did not make generous donations to the presedential election campaign of Nicolas Sarkozy, as Bettencourt did, adding a political twist to the family drama.