Celine Lesage, 38, from Valognes in Normandy, is charged with "aggravated homicide".
She was arrested in 2007 after her partner at the time discovered the corpses in plastic bags in the cellar of their apartment building.
Her lawyer Veronique Carre said Ms Lesage "does not contest the facts."
Several medical and psychological experts are expected to testify in the four-day trial.
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