Lawyers for Teodorin Obiang, the son of Equatorial Guinea's President Teodoro Obiang Nguema, called for his trial to be adjourned when it opened in Paris on Monday.
In the first of what may be several trials of African leaders' relatives, Obiang faces charges of corruption, embezzlement, misuse of public funds and breach of trust.
Obiang's lawyers have fought tooth and nail to prevent the trial taking place, trying to have the charges dropped when they were first made in 2014 on the grounds that he had immunity as his country's junior vice-president and more recently appealing to the International Court of Justice to suspend the legal action against him.
Going into court on Monday they told reporters that Obiang, who was not present and gave his address as his country's capital, Malabo, needed more time to prepare his defence, especially since he intended to call several witnesses who do not live in France.
He has never met the investigators face to face but has been interviewed via a video link.
Obiang could face up to 10 years in prison and the money-laundering charges could lead to a fine of up to a half the sum believed in question, in this case 100 million euros.
A former agriculture and forestry minister, Teodorin Obiang, 47, was promoted to the first vice-presidency in June, putting him in line to succeed his father.
Apartment worth 107 million euros
The inquiry into his assets in France, launched after legal complaints filed by NGOs Sherpa and Transparency International, revealed a lifestyle at odds with the average in a country where more than half of the population live beneath the poverty line:
His luxury residence in Paris's posh avenue Foch is worth 107 million euros and has taps covered in gold leaf, a spa, a discotheque, a gym, a hair salon and a cinema;
A collection of cars including Bugattis, Ferraris and Rolls Royce was hauled away when investigators raided the Paris home in 2011;
He paid upmarket tailors off the Champs Elysées with briefcases full of cash;
Between 2004 and 2011 nearly 110 million euros were paid by Equatorial Guinea's exchequer into his personal account, according to investigators.
Although Obiang says that his income was all legally acquired, prosecutors believe he exploited his position as forestry minister to extract payments from companies investing in precious woods, which along with oil is the country's most valuable natural resource.
Cases in US, Switzerland
His big-spending habits have long been the subject of controversy, notably when he hired the superyacht Tatoosh for an estimated 400,000 dollars (382,000 euros) to impress rap singer Eve and when he spent 10 million rand (696,000 euros) on cars, champagne and property renovations in one weekend in South Africa.
As well as his luxury car collection and property in France, the US and South Africa, he owns a hip-hop record label, TNO Entertainment.
In a 2014 settlement with US prosecutors, Obiang agreed to hand over property worth 30 million dollars (29 million euros), including a villa in the California resort of Malibu, a Ferrari and Michael Jackson memoribilia such as a crystal-covered glove worn by the singer on his 1988 Bad tour worth hundreds of thousands.
The US Justice Department said he "embarked on a corruption-fuelled spending spree in the United States" after racking up 300 million dollars (287 million euros) through embezzlement, extortion and money laundering.
Swiss prosecutors opened a money-laundering case against him in November, seizing 11 luxury cars in Geneva, including a Bugatti Veyron worth around two million euros and a 76-metre yacht, the Ebony Shine.
Precedent for France
The families of several African leaders have extensive properties in France, which has long had close ties to most of the rulers of its former colonies.
Although William Bourdon, a lawyer for Sherpa, has claimed that there "was simply no political will in France" to take up the case initially, cases are now being prepared against the families of several African leaders, including those of Congo's Denis Sasso Nguesso, Gabon's former president Omar Bongo, who is now dead, and the late François Bozizé of the Central African Republic.
Equatorial Guinea, Africa's only Spanish-speaking nation, is the continent's third-biggest oil producer.
The country is regularly criticised by human rights groups for repressive laws, unlawful killings, torture and corruption.