Éric Woerth, who was treasurer for Nicolas Sarkozy’s successful 2007 presidential campaign and then became one of his ministers, was cleared of charges that he exploited Ms. Bettencourt for campaign donations. While Mr. Sarkozy also came under scrutiny in the case, French judges dropped an investigation into charges against him in 2013.

Image Liliane Bettencourt, heiress to the L’Oréal fortune. Credit... Benoit Tessier/Reuters

The case started in 2007, when Ms. Bettencourt’s daughter sued Mr. Banier and accused him of exploiting the heiress’s diminished mental state to obtain millions of euros in gifts, artworks and other favors.

The case captivated France for years. Others were caught in the legal and political developments, especially after it was revealed that Ms. Bettencourt’s butler had secretly recorded dozens of hours of conversations between the heiress and her entourage.

Over all, eight of the 10 defendants in the case, including several of Ms. Bettencourt’s former wealth managers and Mr. Banier’s longtime companion, were found guilty and handed sentences that ranged from heavy fines to prison time.

The case of Alain Thurin, a former nurse for Ms. Bettencourt who attempted to commit suicide on the eve of the trial, will be heard in October.