A woman who claimed that witchcraft caused her to leave her baby to drown on a beach in northern France was on Friday sentenced to 20 years in jail.

Fabienne Kabou, 39, had faced life imprisonment for the November 19, 2013, murder, but the court deemed that she suffered from impaired judgement.

The court in the town of Saint-Omer, near Calais, also ordered Kabou to undergo psychological treatment as it wrapped up her headline-grabbing trial.

Her lawyer, Fabienne Roy-Nansion, expressed dismay over an "extremely heavy" verdict reached after the five-day trial and said Kabou planned to appeal.

The woman of Senegalese origin confessed to travelling from her home near Paris to the town of Berck on the English Channel with the aim of drowning Adelaide, who was 13 months old.

Kabou said she checked the local tide chart before abandoning the baby on the beach as the tide was coming in.

Prawn fishermen found Adelaide's lifeless body the next morning.

Kabou, who grew up in a well-off Catholic family, left Senegal to study philosophy and architecture in Paris, where she fell in love with Michel Lafon, a sculptor 30 years her senior.

Described by her lawyer as highly intelligent, she told the court she had no other explanation for her acts but witchcraft.

"Nothing makes sense in this story. What interest could I have in tormenting myself, lying, killing my daughter?" she asked. "I spoke of sorcery and I am not joking. Even a stupid person would not do what I did."

- Witchcraft claim rejected -

Kabou said she carried out the murder "perfectly mechanically, as if a part of me was anaesthetised" and returned home the next day "with the attitude of someone who has just gone shopping".

She said she had spent some 40,000 euros ($45,000) consulting various "witchdoctors and healers" before carrying out the murder, and that she had suffered hallucinations.

However, a lawyer for a children's group that was a civil party to the case has accused Kabou of citing witchcraft and her native culture as a defence strategy.

An IT expert testified that he found no references to witchcraft on her computer.

A court psychiatrist, Paul Bensussan, said her act was possibly triggered by a deep depression related to having the child.

"Infanticide committed by the mother is often underpinned by a psychiatric pathology," he said. "In most cases the mother is deeply depressed" and sees her act as a kind of "altruistic suicide", saving her child from suffering.

Kabou has said Lafon never wanted the child and questioned whether he was even the father.

Her lawyer said the child was born in the couple's home and was never registered. No one close to the couple, not even Kabou's mother, knew of her existence.

A DNA test carried out after Kabou's arrest confirmed Lafon's paternity.

Source: AFP