Asked in an October 2010 television interview about how he had created the Samsara scent, Guerlain replied using a racial slur – the French term "negre" – and implied that black people are lazy.
"For once, I set to work like a negro. I don't know if negroes have always worked like that, but anyway," he said.
The incident sparked widespread condemnation, with anti-racism groups saying it highlighted deep prejudice in French society.
The 75-year-old heir to one of the world's oldest perfume houses went on trial in February on charges of making "racist insults" during the interview on French public television.
He faces up to six months in prison and a €22,500 ($30,000) fine if the court finds him guilty when it delivers its verdict on Thursday.
And this month French police said they were probing additional accusations that Guerlain made an anti-immigrant rant against Eurostar workers.
Three employees of the high-speed rail firm that links Paris and London made a complaint to police accusing Guerlain of making remarks of a racist nature as they helped the wheelchair-bound pensioner board a train.
Guerlain missed the train because he arrived late at Paris Gare du Nord station and then allegedly launched into a tirade against the three, two of whom were black and the third of Asian origin.
His televised comments last October were quickly denounced, with France's Movement Against Racism and for Friendship (MRAP) saying the remarks revealed "the state of ordinary racism that still permeates French society."
Guerlain apologised but protests erupted outside the company's boutique on the Champs Elysees in Paris and there were calls for a boycott of Guerlain and its owner, luxury brand giant Louis Vuitton Moet Hennessy (LVMH).
"I offer my apologies to all those who might have been hurt by my shocking words," Guerlain said in a statement after the interview. He said the comments "in no way reflect my true thinking, but were a slip of the tongue."
The Guerlain company also distanced itself from the remarks, saying his words were "unacceptable" and noting that Guerlain had not been a shareholder in the company since 1996 or on salary since 2002.
Guerlain took over the family perfume house from his grandfather, Jacques, in 1959, by which time he could reportedly recognise 3,000 subtly different smells.
The perfume house was run by the Guerlain family for five generations and created over 300 fragrances since doctor and chemist Pierre Francois Pascal Guerlain opened his first perfume boutique in Paris 183 years ago.
LVMH purchased the company in 1994 and Guerlain remained as master perfumer until he retired in 2002.
During his time at the company he was hailed as one of the great perfume "noses" of the 20th century and created famous scents including Samsara, Nahema and Jardins de Bagatelle.