A bitter mother-daughter feud, a butler's betrayal, advancing dementia, unscrupulous friends and cash-filled envelopes for politicians: these are only some threads of the complex web surrounding the world's 12th biggest fortune that the court will have to untangle.
The intricate tale began when one of the accused, Francois-Marie Banier, an artist and photographer with a string of rich and famous friends, became a close confidant of Bettencourt, now 92.
The heiress, worth an estimated $38 billion (€33 billion) according to Forbes magazine, showered Banier with gifts, such as paintings by Picasso and Matisse, life insurance funds and millions of euros in cash.
Bettencourt also made him her sole heir, which she would later revoke.
Her daughter Francoise Bettencourt Meyers filed charges against Banier in 2007 for exploiting her mother's growing mental fragility -- which the matriarch staunchly denied -- a month after the death of her father Andre.
Enter the butler.
Concerned about his employer's growing fragility, Pascal Bonnefoy in 2009 placed a recorder in her office, whose explosive contents would reveal her weakened mental state and how she was being manipulated by those around her.
Tax evasion and shady politics
Another one of the accused, Patrice de Maistre, who managed Bettencourt's fortune, is heard in the tapes encouraging her to commit tax evasion -- including hiding the purchase of a Seychelles island, according to media accounts of the recordings.
De Maistre is also accused of getting Bettencourt to hand over envelopes of cash to members of the then-ruling UMP, such as his friend, Eric Woerth, a former minister and campaign treasurer for ex-president Nicolas Sarkozy in his 2007 run for office.
The affair tarnished the latter half of Sarkozy's presidency and when he lost the 2012 election he was placed under formal investigation for illegal campaign financing and taking advantage of Bettencourt.
However the charges were dropped in October 2013, easing the way for Sarkozy to launch a political comeback which saw him win the leadership of the right-wing UMP late last year.
But Woerth is still facing five years in prison and De Maistre is charged with money laundering as well as taking advantage of Bettencourt.
The heiress's former friend, the photographer Banier, is facing three years in prison, and his life partner Martin d'Orgeval is also in the dock in in the southwestern port city of Bordeaux.
A lawyer, a notary, the former manager of Bettencourt's Seychelles island as well as a former nurse to the 92-year-old are also among those accused of exploiting her mental fragility.
As for Bettencourt, the ailing billionaire was in 2011 declared unfit to run her own affairs after a medical report showed she suffered from "mixed dementia" and "moderately severe" Alzheimer's disease.
Her fortune and the cosmetics giant L'Oreal have been placed under the guardianship of family members.
Bettencourt's father Eugene Schueller founded L'Oreal in 1909, starting with hair dye and later branching out to form the world's largest cosmetics company, famous for the advertising slogan, "Because I am Worth it."
Bettencourt, whose own mother died when she was five, started as an apprentice at L'Oreal aged 15 and is no stranger to controversy.
Both her father and her husband Andre Bettencourt were accused of being ardent Nazi collaborators during World War II.