PARIS — Since 2011, when investigators first impounded luxury cars held by the family of Equatorial Guinea’s president, anticorruption groups hoped that France would deal a mortal blow to the injustice they believe has enriched the country’s elites while many of its citizens languish in poverty.

On Wednesday, a judge decided they would have to wait a bit longer.

Three days into the closely watched trial of the president’s son, Teodoro Nguema Obiang Mangue, on embezzlement and money-laundering charges, the presiding judge, Bénédicte de Perthuis, agreed to give the defense more time to prepare. The judge rescheduled the trial for June 19.

Mr. Obiang, known by the nickname Teodorin, is the son of President Teodoro Obiang Nguema Mbasogo, who took power in a 1979 coup and is the longest-serving head of a government in Africa. A former Spanish colony, oil-rich Equatorial Guinea has experienced a boom that started around 2004, but the gains have been far from evenly distributed; half the country lives in poverty.